sphinx.addnodesdocument)}( rawsourcechildren]( translations LanguagesNode)}(hhh](h pending_xref)}(hhh]docutils.nodesTextChinese (Simplified)}parenthsba attributes}(ids]classes]names]dupnames]backrefs] refdomainstdreftypedoc reftarget%/translations/zh_CN/networking/filtermodnameN classnameN refexplicitutagnamehhh ubh)}(hhh]hChinese (Traditional)}hh2sbah}(h]h ]h"]h$]h&] refdomainh)reftypeh+ reftarget%/translations/zh_TW/networking/filtermodnameN classnameN refexplicituh1hhh ubh)}(hhh]hItalian}hhFsbah}(h]h ]h"]h$]h&] refdomainh)reftypeh+ reftarget%/translations/it_IT/networking/filtermodnameN classnameN refexplicituh1hhh ubh)}(hhh]hJapanese}hhZsbah}(h]h ]h"]h$]h&] refdomainh)reftypeh+ reftarget%/translations/ja_JP/networking/filtermodnameN classnameN refexplicituh1hhh ubh)}(hhh]hKorean}hhnsbah}(h]h ]h"]h$]h&] refdomainh)reftypeh+ reftarget%/translations/ko_KR/networking/filtermodnameN classnameN refexplicituh1hhh ubh)}(hhh]hPortuguese (Brazilian)}hhsbah}(h]h ]h"]h$]h&] refdomainh)reftypeh+ reftarget%/translations/pt_BR/networking/filtermodnameN classnameN refexplicituh1hhh ubh)}(hhh]hSpanish}hhsbah}(h]h ]h"]h$]h&] refdomainh)reftypeh+ reftarget%/translations/sp_SP/networking/filtermodnameN classnameN refexplicituh1hhh ubeh}(h]h ]h"]h$]h&]current_languageEnglishuh1h hh _documenthsourceNlineNubhcomment)}(h SPDX-License-Identifier: GPL-2.0h]h SPDX-License-Identifier: GPL-2.0}hhsbah}(h]h ]h"]h$]h&] xml:spacepreserveuh1hhhhhh?/var/lib/git/docbuild/linux/Documentation/networking/filter.rsthKubhtarget)}(h.. _networking-filter:h]h}(h]h ]h"]h$]h&]refidnetworking-filteruh1hhKhhhhhhubhsection)}(hhh](htitle)}(h7Linux Socket Filtering aka Berkeley Packet Filter (BPF)h]h7Linux Socket Filtering aka Berkeley Packet Filter (BPF)}(hhhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhhhhhKubh)}(hhh](h)}(hNoticeh]hNotice}(hhhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhhhhhK ubh paragraph)}(hThis file used to document the eBPF format and mechanisms even when not related to socket filtering. The ../bpf/index.rst has more details on eBPF.h]hThis file used to document the eBPF format and mechanisms even when not related to socket filtering. The ../bpf/index.rst has more details on eBPF.}(hhhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhK hhhhubeh}(h]noticeah ]h"]noticeah$]h&]uh1hhhhhhhhK ubh)}(hhh](h)}(h Introductionh]h Introduction}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhjhhhhhKubh)}(hXLinux Socket Filtering (LSF) is derived from the Berkeley Packet Filter. Though there are some distinct differences between the BSD and Linux Kernel filtering, but when we speak of BPF or LSF in Linux context, we mean the very same mechanism of filtering in the Linux kernel.h]hXLinux Socket Filtering (LSF) is derived from the Berkeley Packet Filter. Though there are some distinct differences between the BSD and Linux Kernel filtering, but when we speak of BPF or LSF in Linux context, we mean the very same mechanism of filtering in the Linux kernel.}(hj%hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjhhubh)}(hXBPF allows a user-space program to attach a filter onto any socket and allow or disallow certain types of data to come through the socket. LSF follows exactly the same filter code structure as BSD's BPF, so referring to the BSD bpf.4 manpage is very helpful in creating filters.h]hXBPF allows a user-space program to attach a filter onto any socket and allow or disallow certain types of data to come through the socket. LSF follows exactly the same filter code structure as BSD’s BPF, so referring to the BSD bpf.4 manpage is very helpful in creating filters.}(hj3hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjhhubh)}(hX5On Linux, BPF is much simpler than on BSD. One does not have to worry about devices or anything like that. You simply create your filter code, send it to the kernel via the SO_ATTACH_FILTER option and if your filter code passes the kernel check on it, you then immediately begin filtering data on that socket.h]hX5On Linux, BPF is much simpler than on BSD. One does not have to worry about devices or anything like that. You simply create your filter code, send it to the kernel via the SO_ATTACH_FILTER option and if your filter code passes the kernel check on it, you then immediately begin filtering data on that socket.}(hjAhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjhhubh)}(hXYou can also detach filters from your socket via the SO_DETACH_FILTER option. This will probably not be used much since when you close a socket that has a filter on it the filter is automagically removed. The other less common case may be adding a different filter on the same socket where you had another filter that is still running: the kernel takes care of removing the old one and placing your new one in its place, assuming your filter has passed the checks, otherwise if it fails the old filter will remain on that socket.h]hXYou can also detach filters from your socket via the SO_DETACH_FILTER option. This will probably not be used much since when you close a socket that has a filter on it the filter is automagically removed. The other less common case may be adding a different filter on the same socket where you had another filter that is still running: the kernel takes care of removing the old one and placing your new one in its place, assuming your filter has passed the checks, otherwise if it fails the old filter will remain on that socket.}(hjOhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhK#hjhhubh)}(hXSO_LOCK_FILTER option allows to lock the filter attached to a socket. Once set, a filter cannot be removed or changed. This allows one process to setup a socket, attach a filter, lock it then drop privileges and be assured that the filter will be kept until the socket is closed.h]hXSO_LOCK_FILTER option allows to lock the filter attached to a socket. Once set, a filter cannot be removed or changed. This allows one process to setup a socket, attach a filter, lock it then drop privileges and be assured that the filter will be kept until the socket is closed.}(hj]hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhK,hjhhubh)}(hXQThe biggest user of this construct might be libpcap. Issuing a high-level filter command like `tcpdump -i em1 port 22` passes through the libpcap internal compiler that generates a structure that can eventually be loaded via SO_ATTACH_FILTER to the kernel. `tcpdump -i em1 port 22 -ddd` displays what is being placed into this structure.h](h^The biggest user of this construct might be libpcap. Issuing a high-level filter command like }(hjkhhhNhNubhtitle_reference)}(h`tcpdump -i em1 port 22`h]htcpdump -i em1 port 22}(hjuhhhNhNubah}(h]h ]h"]h$]h&]uh1jshjkubh passes through the libpcap internal compiler that generates a structure that can eventually be loaded via SO_ATTACH_FILTER to the kernel. }(hjkhhhNhNubjt)}(h`tcpdump -i em1 port 22 -ddd`h]htcpdump -i em1 port 22 -ddd}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1jshjkubh3 displays what is being placed into this structure.}(hjkhhhNhNubeh}(h]h ]h"]h$]h&]uh1hhhhK1hjhhubh)}(hXAlthough we were only speaking about sockets here, BPF in Linux is used in many more places. There's xt_bpf for netfilter, cls_bpf in the kernel qdisc layer, SECCOMP-BPF (SECure COMPuting [1]_), and lots of other places such as team driver, PTP code, etc where BPF is being used.h](hAlthough we were only speaking about sockets here, BPF in Linux is used in many more places. There’s xt_bpf for netfilter, cls_bpf in the kernel qdisc layer, SECCOMP-BPF (SECure COMPuting }(hjhhhNhNubhfootnote_reference)}(h[1]_h]h1}(hjhhhNhNubah}(h]id1ah ]h"]h$]h&]hԌid2docnamenetworking/filteruh1jhjresolvedKubhW), and lots of other places such as team driver, PTP code, etc where BPF is being used.}(hjhhhNhNubeh}(h]h ]h"]h$]h&]uh1hhhhK7hjhhubhfootnote)}(h/Documentation/userspace-api/seccomp_filter.rst h](hlabel)}(h1h]h1}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1jhjubh)}(h.Documentation/userspace-api/seccomp_filter.rsth]h.Documentation/userspace-api/seccomp_filter.rst}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjhhubh)}(hXFSteven McCanne and Van Jacobson. 1993. The BSD packet filter: a new architecture for user-level packet capture. In Proceedings of the USENIX Winter 1993 Conference Proceedings on USENIX Winter 1993 Conference Proceedings (USENIX'93). USENIX Association, Berkeley, CA, USA, 2-2. [http://www.tcpdump.org/papers/bpf-usenix93.pdf]h](hXSteven McCanne and Van Jacobson. 1993. The BSD packet filter: a new architecture for user-level packet capture. In Proceedings of the USENIX Winter 1993 Conference Proceedings on USENIX Winter 1993 Conference Proceedings (USENIX’93). USENIX Association, Berkeley, CA, USA, 2-2. [}(hjhhhNhNubh reference)}(h.http://www.tcpdump.org/papers/bpf-usenix93.pdfh]h.http://www.tcpdump.org/papers/bpf-usenix93.pdf}(hj hhhNhNubah}(h]h ]h"]h$]h&]refurij uh1jhjubh]}(hjhhhNhNubeh}(h]h ]h"]h$]h&]uh1hhhhK@hjhhubeh}(h] introductionah ]h"] introductionah$]h&]uh1hhhhhhhhKubh)}(hhh](h)}(h Structureh]h Structure}(hj-hhhNhNubah}(h]h ]h"]h$]h&]uh1hhj*hhhhhKGubh)}(hcUser space applications include which contains the following relevant structures::h]hbUser space applications include which contains the following relevant structures:}(hj;hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKIhj*hhubh literal_block)}(hstruct sock_filter { /* Filter block */ __u16 code; /* Actual filter code */ __u8 jt; /* Jump true */ __u8 jf; /* Jump false */ __u32 k; /* Generic multiuse field */ };h]hstruct sock_filter { /* Filter block */ __u16 code; /* Actual filter code */ __u8 jt; /* Jump true */ __u8 jf; /* Jump false */ __u32 k; /* Generic multiuse field */ };}hjKsbah}(h]h ]h"]h$]h&]hhuh1jIhhhKLhj*hhubh)}(hSuch a structure is assembled as an array of 4-tuples, that contains a code, jt, jf and k value. jt and jf are jump offsets and k a generic value to be used for a provided code::h]hSuch a structure is assembled as an array of 4-tuples, that contains a code, jt, jf and k value. jt and jf are jump offsets and k a generic value to be used for a provided code:}(hjYhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKShj*hhubjJ)}(hstruct sock_fprog { /* Required for SO_ATTACH_FILTER. */ unsigned short len; /* Number of filter blocks */ struct sock_filter __user *filter; };h]hstruct sock_fprog { /* Required for SO_ATTACH_FILTER. */ unsigned short len; /* Number of filter blocks */ struct sock_filter __user *filter; };}hjgsbah}(h]h ]h"]h$]h&]hhuh1jIhhhKWhj*hhubh)}(hFor socket filtering, a pointer to this structure (as shown in follow-up example) is being passed to the kernel through setsockopt(2).h]hFor socket filtering, a pointer to this structure (as shown in follow-up example) is being passed to the kernel through setsockopt(2).}(hjuhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhK\hj*hhubeh}(h] structureah ]h"] structureah$]h&]uh1hhhhhhhhKGubh)}(hhh](h)}(hExampleh]hExample}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhjhhhhhK`ubjJ)}(hX#include #include #include #include /* ... */ /* From the example above: tcpdump -i em1 port 22 -dd */ struct sock_filter code[] = { { 0x28, 0, 0, 0x0000000c }, { 0x15, 0, 8, 0x000086dd }, { 0x30, 0, 0, 0x00000014 }, { 0x15, 2, 0, 0x00000084 }, { 0x15, 1, 0, 0x00000006 }, { 0x15, 0, 17, 0x00000011 }, { 0x28, 0, 0, 0x00000036 }, { 0x15, 14, 0, 0x00000016 }, { 0x28, 0, 0, 0x00000038 }, { 0x15, 12, 13, 0x00000016 }, { 0x15, 0, 12, 0x00000800 }, { 0x30, 0, 0, 0x00000017 }, { 0x15, 2, 0, 0x00000084 }, { 0x15, 1, 0, 0x00000006 }, { 0x15, 0, 8, 0x00000011 }, { 0x28, 0, 0, 0x00000014 }, { 0x45, 6, 0, 0x00001fff }, { 0xb1, 0, 0, 0x0000000e }, { 0x48, 0, 0, 0x0000000e }, { 0x15, 2, 0, 0x00000016 }, { 0x48, 0, 0, 0x00000010 }, { 0x15, 0, 1, 0x00000016 }, { 0x06, 0, 0, 0x0000ffff }, { 0x06, 0, 0, 0x00000000 }, }; struct sock_fprog bpf = { .len = ARRAY_SIZE(code), .filter = code, }; sock = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_ALL)); if (sock < 0) /* ... bail out ... */ ret = setsockopt(sock, SOL_SOCKET, SO_ATTACH_FILTER, &bpf, sizeof(bpf)); if (ret < 0) /* ... bail out ... */ /* ... */ close(sock);h]hX#include #include #include #include /* ... */ /* From the example above: tcpdump -i em1 port 22 -dd */ struct sock_filter code[] = { { 0x28, 0, 0, 0x0000000c }, { 0x15, 0, 8, 0x000086dd }, { 0x30, 0, 0, 0x00000014 }, { 0x15, 2, 0, 0x00000084 }, { 0x15, 1, 0, 0x00000006 }, { 0x15, 0, 17, 0x00000011 }, { 0x28, 0, 0, 0x00000036 }, { 0x15, 14, 0, 0x00000016 }, { 0x28, 0, 0, 0x00000038 }, { 0x15, 12, 13, 0x00000016 }, { 0x15, 0, 12, 0x00000800 }, { 0x30, 0, 0, 0x00000017 }, { 0x15, 2, 0, 0x00000084 }, { 0x15, 1, 0, 0x00000006 }, { 0x15, 0, 8, 0x00000011 }, { 0x28, 0, 0, 0x00000014 }, { 0x45, 6, 0, 0x00001fff }, { 0xb1, 0, 0, 0x0000000e }, { 0x48, 0, 0, 0x0000000e }, { 0x15, 2, 0, 0x00000016 }, { 0x48, 0, 0, 0x00000010 }, { 0x15, 0, 1, 0x00000016 }, { 0x06, 0, 0, 0x0000ffff }, { 0x06, 0, 0, 0x00000000 }, }; struct sock_fprog bpf = { .len = ARRAY_SIZE(code), .filter = code, }; sock = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_ALL)); if (sock < 0) /* ... bail out ... */ ret = setsockopt(sock, SOL_SOCKET, SO_ATTACH_FILTER, &bpf, sizeof(bpf)); if (ret < 0) /* ... bail out ... */ /* ... */ close(sock);}hjsbah}(h]h ]h"]h$]h&]hhuh1jIhhhKdhjhhubh)}(hThe above example code attaches a socket filter for a PF_PACKET socket in order to let all IPv4/IPv6 packets with port 22 pass. The rest will be dropped for this socket.h]hThe above example code attaches a socket filter for a PF_PACKET socket in order to let all IPv4/IPv6 packets with port 22 pass. The rest will be dropped for this socket.}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjhhubh)}(hThe setsockopt(2) call to SO_DETACH_FILTER doesn't need any arguments and SO_LOCK_FILTER for preventing the filter to be detached, takes an integer value with 0 or 1.h]hThe setsockopt(2) call to SO_DETACH_FILTER doesn’t need any arguments and SO_LOCK_FILTER for preventing the filter to be detached, takes an integer value with 0 or 1.}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjhhubh)}(huNote that socket filters are not restricted to PF_PACKET sockets only, but can also be used on other socket families.h]huNote that socket filters are not restricted to PF_PACKET sockets only, but can also be used on other socket families.}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjhhubh)}(hSummary of system calls:h]hSummary of system calls:}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjhhubh block_quote)}(h* setsockopt(sockfd, SOL_SOCKET, SO_ATTACH_FILTER, &val, sizeof(val)); * setsockopt(sockfd, SOL_SOCKET, SO_DETACH_FILTER, &val, sizeof(val)); * setsockopt(sockfd, SOL_SOCKET, SO_LOCK_FILTER, &val, sizeof(val)); h]h bullet_list)}(hhh](h list_item)}(hDsetsockopt(sockfd, SOL_SOCKET, SO_ATTACH_FILTER, &val, sizeof(val));h]h)}(hjh]hDsetsockopt(sockfd, SOL_SOCKET, SO_ATTACH_FILTER, &val, sizeof(val));}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjubah}(h]h ]h"]h$]h&]uh1jhjubj)}(hDsetsockopt(sockfd, SOL_SOCKET, SO_DETACH_FILTER, &val, sizeof(val));h]h)}(hjh]hDsetsockopt(sockfd, SOL_SOCKET, SO_DETACH_FILTER, &val, sizeof(val));}(hj hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjubah}(h]h ]h"]h$]h&]uh1jhjubj)}(hEsetsockopt(sockfd, SOL_SOCKET, SO_LOCK_FILTER, &val, sizeof(val)); h]h)}(hDsetsockopt(sockfd, SOL_SOCKET, SO_LOCK_FILTER, &val, sizeof(val));h]hDsetsockopt(sockfd, SOL_SOCKET, SO_LOCK_FILTER, &val, sizeof(val));}(hj!hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjubah}(h]h ]h"]h$]h&]uh1jhjubeh}(h]h ]h"]h$]h&]bullet*uh1jhhhKhjubah}(h]h ]h"]h$]h&]uh1jhhhKhjhhubh)}(hNormally, most use cases for socket filtering on packet sockets will be covered by libpcap in high-level syntax, so as an application developer you should stick to that. libpcap wraps its own layer around all that.h]hNormally, most use cases for socket filtering on packet sockets will be covered by libpcap in high-level syntax, so as an application developer you should stick to that. libpcap wraps its own layer around all that.}(hjChhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjhhubh)}(hXUnless i) using/linking to libpcap is not an option, ii) the required BPF filters use Linux extensions that are not supported by libpcap's compiler, iii) a filter might be more complex and not cleanly implementable with libpcap's compiler, or iv) particular filter codes should be optimized differently than libpcap's internal compiler does; then in such cases writing such a filter "by hand" can be of an alternative. For example, xt_bpf and cls_bpf users might have requirements that could result in more complex filter code, or one that cannot be expressed with libpcap (e.g. different return codes for various code paths). Moreover, BPF JIT implementors may wish to manually write test cases and thus need low-level access to BPF code as well.h]hXUnless i) using/linking to libpcap is not an option, ii) the required BPF filters use Linux extensions that are not supported by libpcap’s compiler, iii) a filter might be more complex and not cleanly implementable with libpcap’s compiler, or iv) particular filter codes should be optimized differently than libpcap’s internal compiler does; then in such cases writing such a filter “by hand” can be of an alternative. For example, xt_bpf and cls_bpf users might have requirements that could result in more complex filter code, or one that cannot be expressed with libpcap (e.g. different return codes for various code paths). Moreover, BPF JIT implementors may wish to manually write test cases and thus need low-level access to BPF code as well.}(hjQhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjhhubeh}(h]exampleah ]h"]exampleah$]h&]uh1hhhhhhhhK`ubh)}(hhh](h)}(hBPF engine and instruction seth]hBPF engine and instruction set}(hjjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhjghhhhhKubh)}(hThe examples below use an assembly notation instead of less readable opcodes. The notation is closely modelled after Steven McCanne's and Van Jacobson's BPF paper.h]hThe examples below use an assembly notation instead of less readable opcodes. The notation is closely modelled after Steven McCanne’s and Van Jacobson’s BPF paper.}(hjxhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjghhubh)}(h>The BPF architecture consists of the following basic elements:h]h>The BPF architecture consists of the following basic elements:}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjghhubj)}(hX======= ==================================================== Element Description ======= ==================================================== A 32 bit wide accumulator X 32 bit wide X register M[] 16 x 32 bit wide misc registers aka "scratch memory store", addressable from 0 to 15 ======= ==================================================== h]htable)}(hhh]htgroup)}(hhh](hcolspec)}(hhh]h}(h]h ]h"]h$]h&]colwidthKuh1jhjubj)}(hhh]h}(h]h ]h"]h$]h&]colwidthK4uh1jhjubhthead)}(hhh]hrow)}(hhh](hentry)}(hhh]h)}(hElementh]hElement}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjubah}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh]h)}(h Descriptionh]h Description}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjubah}(h]h ]h"]h$]h&]uh1jhjubeh}(h]h ]h"]h$]h&]uh1jhjubah}(h]h ]h"]h$]h&]uh1jhjubhtbody)}(hhh](j)}(hhh](j)}(hhh]h)}(hAh]hA}(hj hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjubah}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh]h)}(h32 bit wide accumulatorh]h32 bit wide accumulator}(hj hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjubah}(h]h ]h"]h$]h&]uh1jhjubeh}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh](j)}(hhh]h)}(hXh]hX}(hj@hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj=ubah}(h]h ]h"]h$]h&]uh1jhj:ubj)}(hhh]h)}(h32 bit wide X registerh]h32 bit wide X register}(hjWhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjTubah}(h]h ]h"]h$]h&]uh1jhj:ubeh}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh](j)}(hhh]h)}(hM[]h]hM[]}(hjwhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjtubah}(h]h ]h"]h$]h&]uh1jhjqubj)}(hhh]h)}(hT16 x 32 bit wide misc registers aka "scratch memory store", addressable from 0 to 15h]hX16 x 32 bit wide misc registers aka “scratch memory store”, addressable from 0 to 15}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjubah}(h]h ]h"]h$]h&]uh1jhjqubeh}(h]h ]h"]h$]h&]uh1jhjubeh}(h]h ]h"]h$]h&]uh1jhjubeh}(h]h ]h"]h$]h&]colsKuh1jhjubah}(h]h ]h"]h$]h&]uh1jhjubah}(h]h ]h"]h$]h&]uh1jhhhKhjghhubh)}(h^A BPF program is an array of instructions with the following elements (as already mentioned)::h]h]A BPF program is an array of instructions with the following elements (as already mentioned):}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjghhubjJ)}(hop:16, jt:8, jf:8, k:32h]hop:16, jt:8, jf:8, k:32}hjsbah}(h]h ]h"]h$]h&]hhuh1jIhhhKhjghhubh)}(hXIThe element op is a 16 bit wide opcode that has a particular instruction encoded. jt and jf are two 8 bit wide jump targets, one for condition "jump if true", the other one "jump if false". Eventually, element k contains a miscellaneous argument that can be interpreted in different ways depending on the given instruction in op.h]hXQThe element op is a 16 bit wide opcode that has a particular instruction encoded. jt and jf are two 8 bit wide jump targets, one for condition “jump if true”, the other one “jump if false”. Eventually, element k contains a miscellaneous argument that can be interpreted in different ways depending on the given instruction in op.}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjghhubh)}(hThe instruction set consists of load, store, branch, alu, miscellaneous and return instructions. This table lists the assembly notation and what the corresponding opcodes defined in linux/filter.h do:h]hThe instruction set consists of load, store, branch, alu, miscellaneous and return instructions. This table lists the assembly notation and what the corresponding opcodes defined in linux/filter.h do:}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjghhubj)}(hX=========== =================== ===================== Instruction Addressing mode Description =========== =================== ===================== ld 1, 2, 3, 4, 12 Load word into A ldi 4 Load word into A ldh 1, 2 Load half-word into A ldb 1, 2 Load byte into A ldx 3, 4, 5, 12 Load word into X ldxi 4 Load word into X ldxb 5 Load byte into X st 3 Store A into M[] stx 3 Store X into M[] jmp 6 Jump to label ja 6 Jump to label jeq 7, 8, 9, 10 Jump on A == jneq 9, 10 Jump on A != jne 9, 10 Jump on A != jlt 9, 10 Jump on A < jle 9, 10 Jump on A <= jgt 7, 8, 9, 10 Jump on A > jge 7, 8, 9, 10 Jump on A >= jset 7, 8, 9, 10 Jump on A & add 0, 4 A + sub 0, 4 A - mul 0, 4 A * div 0, 4 A / mod 0, 4 A % neg !A and 0, 4 A & or 0, 4 A | xor 0, 4 A ^ lsh 0, 4 A << rsh 0, 4 A >> tax Copy A into X txa Copy X into A ret 4, 11 Return =========== =================== ===================== h]j)}(hhh]j)}(hhh](j)}(hhh]h}(h]h ]h"]h$]h&]colwidthK uh1jhjubj)}(hhh]h}(h]h ]h"]h$]h&]colwidthKuh1jhjubj)}(hhh]h}(h]h ]h"]h$]h&]colwidthKuh1jhjubj)}(hhh]j)}(hhh](j)}(hhh]h)}(h Instructionh]h Instruction}(hj*hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj'ubah}(h]h ]h"]h$]h&]uh1jhj$ubj)}(hhh]h)}(hAddressing modeh]hAddressing mode}(hjAhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj>ubah}(h]h ]h"]h$]h&]uh1jhj$ubj)}(hhh]h)}(h Descriptionh]h Description}(hjXhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjUubah}(h]h ]h"]h$]h&]uh1jhj$ubeh}(h]h ]h"]h$]h&]uh1jhj!ubah}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh](j)}(hhh](j)}(hhh]h)}(hldh]hld}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj~ubah}(h]h ]h"]h$]h&]uh1jhj{ubj)}(hhh]h)}(h1, 2, 3, 4, 12h]h1, 2, 3, 4, 12}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjubah}(h]h ]h"]h$]h&]uh1jhj{ubj)}(hhh]h)}(hLoad word into Ah]hLoad word into A}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjubah}(h]h ]h"]h$]h&]uh1jhj{ubeh}(h]h ]h"]h$]h&]uh1jhjxubj)}(hhh](j)}(hhh]h)}(hldih]hldi}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjubah}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh]h)}(h4h]h4}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjubah}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh]h)}(hLoad word into Ah]hLoad word into A}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjubah}(h]h ]h"]h$]h&]uh1jhjubeh}(h]h ]h"]h$]h&]uh1jhjxubj)}(hhh](j)}(hhh]h)}(hldhh]hldh}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjubah}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh]h)}(h1, 2h]h1, 2}(hj4hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj1ubah}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh]h)}(hLoad half-word into Ah]hLoad half-word into A}(hjKhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjHubah}(h]h ]h"]h$]h&]uh1jhjubeh}(h]h ]h"]h$]h&]uh1jhjxubj)}(hhh](j)}(hhh]h)}(hldbh]hldb}(hjkhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjhubah}(h]h ]h"]h$]h&]uh1jhjeubj)}(hhh]h)}(h1, 2h]h1, 2}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjubah}(h]h ]h"]h$]h&]uh1jhjeubj)}(hhh]h)}(hLoad byte into Ah]hLoad byte into A}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjubah}(h]h ]h"]h$]h&]uh1jhjeubeh}(h]h ]h"]h$]h&]uh1jhjxubj)}(hhh](j)}(hhh]h)}(hldxh]hldx}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjubah}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh]h)}(h 3, 4, 5, 12h]h 3, 4, 5, 12}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjubah}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh]h)}(hLoad word into Xh]hLoad word into X}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjubah}(h]h ]h"]h$]h&]uh1jhjubeh}(h]h ]h"]h$]h&]uh1jhjxubj)}(hhh](j)}(hhh]h)}(hldxih]hldxi}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjubah}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh]h)}(hjh]h4}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjubah}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh]h)}(hLoad word into Xh]hLoad word into X}(hj4hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj1ubah}(h]h ]h"]h$]h&]uh1jhjubeh}(h]h ]h"]h$]h&]uh1jhjxubj)}(hhh](j)}(hhh]h)}(hldxbh]hldxb}(hjThhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjQubah}(h]h ]h"]h$]h&]uh1jhjNubj)}(hhh]h)}(h5h]h5}(hjkhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjhubah}(h]h ]h"]h$]h&]uh1jhjNubj)}(hhh]h)}(hLoad byte into Xh]hLoad byte into X}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjubah}(h]h ]h"]h$]h&]uh1jhjNubeh}(h]h ]h"]h$]h&]uh1jhjxubj)}(hhh](j)}(hhh]h)}(hsth]hst}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjubah}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh]h)}(h3h]h3}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjubah}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh]h)}(hStore A into M[]h]hStore A into M[]}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjubah}(h]h ]h"]h$]h&]uh1jhjubeh}(h]h ]h"]h$]h&]uh1jhjxubj)}(hhh](j)}(hhh]h)}(hstxh]hstx}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjubah}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh]h)}(hjh]h3}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjubah}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh]h)}(hStore X into M[]h]hStore X into M[]}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjubah}(h]h ]h"]h$]h&]uh1jhjubeh}(h]h ]h"]h$]h&]uh1jhjxubj)}(hhh](j)}(hhh]h)}(hjmph]hjmp}(hj=hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj:ubah}(h]h ]h"]h$]h&]uh1jhj7ubj)}(hhh]h)}(h6h]h6}(hjThhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjQubah}(h]h ]h"]h$]h&]uh1jhj7ubj)}(hhh]h)}(h Jump to labelh]h Jump to label}(hjkhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjhubah}(h]h ]h"]h$]h&]uh1jhj7ubeh}(h]h ]h"]h$]h&]uh1jhjxubj)}(hhh](j)}(hhh]h)}(hjah]hja}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjubah}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh]h)}(hjVh]h6}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjubah}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh]h)}(h Jump to labelh]h Jump to label}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjubah}(h]h ]h"]h$]h&]uh1jhjubeh}(h]h ]h"]h$]h&]uh1jhjxubj)}(hhh](j)}(hhh]h)}(hjeqh]hjeq}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjubah}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh]h)}(h 7, 8, 9, 10h]h 7, 8, 9, 10}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjubah}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh]h)}(hJump on A == h]hJump on A == }(hj hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj ubah}(h]h ]h"]h$]h&]uh1jhjubeh}(h]h ]h"]h$]h&]uh1jhjxubj)}(hhh](j)}(hhh]h)}(hjneqh]hjneq}(hj& hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj# ubah}(h]h ]h"]h$]h&]uh1jhj ubj)}(hhh]h)}(h9, 10h]h9, 10}(hj= hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj: ubah}(h]h ]h"]h$]h&]uh1jhj ubj)}(hhh]h)}(hJump on A != h]hJump on A != }(hjT hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjQ ubah}(h]h ]h"]h$]h&]uh1jhj ubeh}(h]h ]h"]h$]h&]uh1jhjxubj)}(hhh](j)}(hhh]h)}(hjneh]hjne}(hjt hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjq ubah}(h]h ]h"]h$]h&]uh1jhjn ubj)}(hhh]h)}(h9, 10h]h9, 10}(hj hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj ubah}(h]h ]h"]h$]h&]uh1jhjn ubj)}(hhh]h)}(hJump on A != h]hJump on A != }(hj hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj ubah}(h]h ]h"]h$]h&]uh1jhjn ubeh}(h]h ]h"]h$]h&]uh1jhjxubj)}(hhh](j)}(hhh]h)}(hjlth]hjlt}(hj hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj ubah}(h]h ]h"]h$]h&]uh1jhj ubj)}(hhh]h)}(h9, 10h]h9, 10}(hj hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj ubah}(h]h ]h"]h$]h&]uh1jhj ubj)}(hhh]h)}(hJump on A < h]hJump on A < }(hj hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj ubah}(h]h ]h"]h$]h&]uh1jhj ubeh}(h]h ]h"]h$]h&]uh1jhjxubj)}(hhh](j)}(hhh]h)}(hjleh]hjle}(hj hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj ubah}(h]h ]h"]h$]h&]uh1jhj ubj)}(hhh]h)}(h9, 10h]h9, 10}(hj' hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj$ ubah}(h]h ]h"]h$]h&]uh1jhj ubj)}(hhh]h)}(hJump on A <= h]hJump on A <= }(hj> hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj; ubah}(h]h ]h"]h$]h&]uh1jhj ubeh}(h]h ]h"]h$]h&]uh1jhjxubj)}(hhh](j)}(hhh]h)}(hjgth]hjgt}(hj^ hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj[ ubah}(h]h ]h"]h$]h&]uh1jhjX ubj)}(hhh]h)}(h 7, 8, 9, 10h]h 7, 8, 9, 10}(hju hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjr ubah}(h]h ]h"]h$]h&]uh1jhjX ubj)}(hhh]h)}(hJump on A > h]hJump on A > }(hj hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj ubah}(h]h ]h"]h$]h&]uh1jhjX ubeh}(h]h ]h"]h$]h&]uh1jhjxubj)}(hhh](j)}(hhh]h)}(hjgeh]hjge}(hj hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj ubah}(h]h ]h"]h$]h&]uh1jhj ubj)}(hhh]h)}(h 7, 8, 9, 10h]h 7, 8, 9, 10}(hj hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj ubah}(h]h ]h"]h$]h&]uh1jhj ubj)}(hhh]h)}(hJump on A >= h]hJump on A >= }(hj hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj ubah}(h]h ]h"]h$]h&]uh1jhj ubeh}(h]h ]h"]h$]h&]uh1jhjxubj)}(hhh](j)}(hhh]h)}(hjseth]hjset}(hj hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj ubah}(h]h ]h"]h$]h&]uh1jhj ubj)}(hhh]h)}(h 7, 8, 9, 10h]h 7, 8, 9, 10}(hj hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj ubah}(h]h ]h"]h$]h&]uh1jhj ubj)}(hhh]h)}(hJump on A & h]hJump on A & }(hj( hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj% ubah}(h]h ]h"]h$]h&]uh1jhj ubeh}(h]h ]h"]h$]h&]uh1jhjxubj)}(hhh](j)}(hhh]h)}(haddh]hadd}(hjH hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjE ubah}(h]h ]h"]h$]h&]uh1jhjB ubj)}(hhh]h)}(h0, 4h]h0, 4}(hj_ hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj\ ubah}(h]h ]h"]h$]h&]uh1jhjB ubj)}(hhh]h)}(hA + h]hA + }(hjv hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjs ubah}(h]h ]h"]h$]h&]uh1jhjB ubeh}(h]h ]h"]h$]h&]uh1jhjxubj)}(hhh](j)}(hhh]h)}(hsubh]hsub}(hj hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj ubah}(h]h ]h"]h$]h&]uh1jhj ubj)}(hhh]h)}(h0, 4h]h0, 4}(hj hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj ubah}(h]h ]h"]h$]h&]uh1jhj ubj)}(hhh]h)}(hA - h]hA - }(hj hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj ubah}(h]h ]h"]h$]h&]uh1jhj ubeh}(h]h ]h"]h$]h&]uh1jhjxubj)}(hhh](j)}(hhh]h)}(hmulh]hmul}(hj hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj ubah}(h]h ]h"]h$]h&]uh1jhj ubj)}(hhh]h)}(h0, 4h]h0, 4}(hj hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj ubah}(h]h ]h"]h$]h&]uh1jhj ubj)}(hhh]h)}(hA * h]hA * }(hj hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj ubah}(h]h ]h"]h$]h&]uh1jhj ubeh}(h]h ]h"]h$]h&]uh1jhjxubj)}(hhh](j)}(hhh]h)}(hdivh]hdiv}(hj2 hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj/ ubah}(h]h ]h"]h$]h&]uh1jhj, ubj)}(hhh]h)}(h0, 4h]h0, 4}(hjI hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjF ubah}(h]h ]h"]h$]h&]uh1jhj, ubj)}(hhh]h)}(hA / h]hA / }(hj` hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj] ubah}(h]h ]h"]h$]h&]uh1jhj, ubeh}(h]h ]h"]h$]h&]uh1jhjxubj)}(hhh](j)}(hhh]h)}(hmodh]hmod}(hj hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj} ubah}(h]h ]h"]h$]h&]uh1jhjz ubj)}(hhh]h)}(h0, 4h]h0, 4}(hj hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj ubah}(h]h ]h"]h$]h&]uh1jhjz ubj)}(hhh]h)}(hA % h]hA % }(hj hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj ubah}(h]h ]h"]h$]h&]uh1jhjz ubeh}(h]h ]h"]h$]h&]uh1jhjxubj)}(hhh](j)}(hhh]h)}(hnegh]hneg}(hj hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj ubah}(h]h ]h"]h$]h&]uh1jhj ubj)}(hhh]h}(h]h ]h"]h$]h&]uh1jhj ubj)}(hhh]h)}(h!Ah]h!A}(hj hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj ubah}(h]h ]h"]h$]h&]uh1jhj ubeh}(h]h ]h"]h$]h&]uh1jhjxubj)}(hhh](j)}(hhh]h)}(handh]hand}(hj hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj ubah}(h]h ]h"]h$]h&]uh1jhj ubj)}(hhh]h)}(h0, 4h]h0, 4}(hj% hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj" ubah}(h]h ]h"]h$]h&]uh1jhj ubj)}(hhh]h)}(hA & h]hA & }(hj< hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj9 ubah}(h]h ]h"]h$]h&]uh1jhj ubeh}(h]h ]h"]h$]h&]uh1jhjxubj)}(hhh](j)}(hhh]h)}(horh]hor}(hj\ hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjY ubah}(h]h ]h"]h$]h&]uh1jhjV ubj)}(hhh]h)}(h0, 4h]h0, 4}(hjs hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjp ubah}(h]h ]h"]h$]h&]uh1jhjV ubj)}(hhh]h)}(hA | h]hA | }(hj hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj ubah}(h]h ]h"]h$]h&]uh1jhjV ubeh}(h]h ]h"]h$]h&]uh1jhjxubj)}(hhh](j)}(hhh]h)}(hxorh]hxor}(hj hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj ubah}(h]h ]h"]h$]h&]uh1jhj ubj)}(hhh]h)}(h0, 4h]h0, 4}(hj hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj ubah}(h]h ]h"]h$]h&]uh1jhj ubj)}(hhh]h)}(hA ^ h]hA ^ }(hj hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj ubah}(h]h ]h"]h$]h&]uh1jhj ubeh}(h]h ]h"]h$]h&]uh1jhjxubj)}(hhh](j)}(hhh]h)}(hlshh]hlsh}(hj hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj ubah}(h]h ]h"]h$]h&]uh1jhj ubj)}(hhh]h)}(h0, 4h]h0, 4}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj ubah}(h]h ]h"]h$]h&]uh1jhj ubj)}(hhh]h)}(hA << h]hA << }(hj&hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhj#ubah}(h]h ]h"]h$]h&]uh1jhj ubeh}(h]h ]h"]h$]h&]uh1jhjxubj)}(hhh](j)}(hhh]h)}(hrshh]hrsh}(hjFhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjCubah}(h]h ]h"]h$]h&]uh1jhj@ubj)}(hhh]h)}(h0, 4h]h0, 4}(hj]hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjZubah}(h]h ]h"]h$]h&]uh1jhj@ubj)}(hhh]h)}(hA >> h]hA >> }(hjthhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjqubah}(h]h ]h"]h$]h&]uh1jhj@ubeh}(h]h ]h"]h$]h&]uh1jhjxubj)}(hhh](j)}(hhh]h)}(htaxh]htax}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjubah}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh]h}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh]h)}(h Copy A into Xh]h Copy A into X}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjubah}(h]h ]h"]h$]h&]uh1jhjubeh}(h]h ]h"]h$]h&]uh1jhjxubj)}(hhh](j)}(hhh]h)}(htxah]htxa}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjubah}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh]h}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh]h)}(h Copy X into Ah]h Copy X into A}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhKhjubah}(h]h ]h"]h$]h&]uh1jhjubeh}(h]h ]h"]h$]h&]uh1jhjxubj)}(hhh](j)}(hhh]h)}(hreth]hret}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhMhjubah}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh]h)}(h4, 11h]h4, 11}(hj+hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhMhj(ubah}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh]h)}(hReturnh]hReturn}(hjBhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhMhj?ubah}(h]h ]h"]h$]h&]uh1jhjubeh}(h]h ]h"]h$]h&]uh1jhjxubeh}(h]h ]h"]h$]h&]uh1jhjubeh}(h]h ]h"]h$]h&]colsKuh1jhjubah}(h]h ]h"]h$]h&]uh1jhjubah}(h]h ]h"]h$]h&]uh1jhhhKhjghhubh)}(hubah}(h]h ]h"]h$]h&]uh1jhj ubeh}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh](j)}(hhh]h)}(h11h]h11}(hjahhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhMhj^ubah}(h]h ]h"]h$]h&]uh1jhj[ubj)}(hhh]h)}(ha/%ah]ha/%a}(hjxhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhMhjuubah}(h]h ]h"]h$]h&]uh1jhj[ubj)}(hhh]h)}(h Accumulator Ah]h Accumulator A}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhMhjubah}(h]h ]h"]h$]h&]uh1jhj[ubeh}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh](j)}(hhh]h)}(h12h]h12}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhMhjubah}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh]h)}(h extensionh]h extension}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhMhjubah}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh]h)}(h BPF extensionh]h BPF extension}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhMhjubah}(h]h ]h"]h$]h&]uh1jhjubeh}(h]h ]h"]h$]h&]uh1jhjubeh}(h]h ]h"]h$]h&]uh1jhjubeh}(h]h ]h"]h$]h&]colsKuh1jhjubah}(h]h ]h"]h$]h&]uh1jhjubah}(h]h ]h"]h$]h&]uh1jhhhMhjghhubh)}(hThe Linux kernel also has a couple of BPF extensions that are used along with the class of load instructions by "overloading" the k argument with a negative offset + a particular extension offset. The result of such BPF extensions are loaded into A.h]hThe Linux kernel also has a couple of BPF extensions that are used along with the class of load instructions by “overloading” the k argument with a negative offset + a particular extension offset. The result of such BPF extensions are loaded into A.}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhMhjghhubh)}(h9Possible BPF extensions are shown in the following table:h]h9Possible BPF extensions are shown in the following table:}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhMhjghhubj)}(hX=================================== ================================================= Extension Description =================================== ================================================= len skb->len proto skb->protocol type skb->pkt_type poff Payload start offset ifidx skb->dev->ifindex nla Netlink attribute of type X with offset A nlan Nested Netlink attribute of type X with offset A mark skb->mark queue skb->queue_mapping hatype skb->dev->type rxhash skb->hash cpu raw_smp_processor_id() vlan_tci skb_vlan_tag_get(skb) vlan_avail skb_vlan_tag_present(skb) vlan_tpid skb->vlan_proto rand get_random_u32() =================================== ================================================= h]j)}(hhh]j)}(hhh](j)}(hhh]h}(h]h ]h"]h$]h&]colwidthK#uh1jhj3ubj)}(hhh]h}(h]h ]h"]h$]h&]colwidthK1uh1jhj3ubj)}(hhh]j)}(hhh](j)}(hhh]h)}(h Extensionh]h Extension}(hjShhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhMhjPubah}(h]h ]h"]h$]h&]uh1jhjMubj)}(hhh]h)}(h Descriptionh]h Description}(hjjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhMhjgubah}(h]h ]h"]h$]h&]uh1jhjMubeh}(h]h ]h"]h$]h&]uh1jhjJubah}(h]h ]h"]h$]h&]uh1jhj3ubj)}(hhh](j)}(hhh](j)}(hhh]h)}(hlenh]hlen}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhM!hjubah}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh]h)}(hskb->lenh]hskb->len}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhM!hjubah}(h]h ]h"]h$]h&]uh1jhjubeh}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh](j)}(hhh]h)}(hprotoh]hproto}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhM"hjubah}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh]h)}(h skb->protocolh]h skb->protocol}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhM"hjubah}(h]h ]h"]h$]h&]uh1jhjubeh}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh](j)}(hhh]h)}(htypeh]htype}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhM#hjubah}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh]h)}(h skb->pkt_typeh]h skb->pkt_type}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhM#hjubah}(h]h ]h"]h$]h&]uh1jhjubeh}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh](j)}(hhh]h)}(hpoffh]hpoff}(hj8hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhM$hj5ubah}(h]h ]h"]h$]h&]uh1jhj2ubj)}(hhh]h)}(hPayload start offseth]hPayload start offset}(hjOhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhM$hjLubah}(h]h ]h"]h$]h&]uh1jhj2ubeh}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh](j)}(hhh]h)}(hifidxh]hifidx}(hjohhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhM%hjlubah}(h]h ]h"]h$]h&]uh1jhjiubj)}(hhh]h)}(hskb->dev->ifindexh]hskb->dev->ifindex}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhM%hjubah}(h]h ]h"]h$]h&]uh1jhjiubeh}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh](j)}(hhh]h)}(hnlah]hnla}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhM&hjubah}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh]h)}(h)Netlink attribute of type X with offset Ah]h)Netlink attribute of type X with offset A}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhM&hjubah}(h]h ]h"]h$]h&]uh1jhjubeh}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh](j)}(hhh]h)}(hnlanh]hnlan}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhM'hjubah}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh]h)}(h0Nested Netlink attribute of type X with offset Ah]h0Nested Netlink attribute of type X with offset A}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhM'hjubah}(h]h ]h"]h$]h&]uh1jhjubeh}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh](j)}(hhh]h)}(hmarkh]hmark}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhM(hjubah}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh]h)}(h skb->markh]h skb->mark}(hj+hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhM(hj(ubah}(h]h ]h"]h$]h&]uh1jhjubeh}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh](j)}(hhh]h)}(hqueueh]hqueue}(hjKhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhM)hjHubah}(h]h ]h"]h$]h&]uh1jhjEubj)}(hhh]h)}(hskb->queue_mappingh]hskb->queue_mapping}(hjbhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhM)hj_ubah}(h]h ]h"]h$]h&]uh1jhjEubeh}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh](j)}(hhh]h)}(hhatypeh]hhatype}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhM*hjubah}(h]h ]h"]h$]h&]uh1jhj|ubj)}(hhh]h)}(hskb->dev->typeh]hskb->dev->type2[}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhM*hjubah}(h]h ]h"]h$]h&]uh1jhj|ubeh}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh](j)}(hhh]h)}(hrxhashh]hrxhash}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhM+hjubah}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh]h)}(h skb->hashh]h skb->hash}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhM+hjubah}(h]h ]h"]h$]h&]uh1jhjubeh}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh](j)}(hhh]h)}(hcpuh]hcpu}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhM,hjubah}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh]h)}(hraw_smp_processor_id()h]hraw_smp_processor_id()}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhM,hjubah}(h]h ]h"]h$]h&]uh1jhjubeh}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh](j)}(hhh]h)}(hvlan_tcih]hvlan_tci}(hj'hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhM-hj$ubah}(h]h ]h"]h$]h&]uh1jhj!ubj)}(hhh]h)}(hskb_vlan_tag_get(skb)h]hskb_vlan_tag_get(skb)}(hj>hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhM-hj;ubah}(h]h ]h"]h$]h&]uh1jhj!ubeh}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh](j)}(hhh]h)}(h vlan_availh]h vlan_avail}(hj^hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhM.hj[ubah}(h]h ]h"]h$]h&]uh1jhjXubj)}(hhh]h)}(hskb_vlan_tag_present(skb)h]hskb_vlan_tag_present(skb)}(hjuhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhM.hjrubah}(h]h ]h"]h$]h&]uh1jhjXubeh}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh](j)}(hhh]h)}(h vlan_tpidh]h vlan_tpid}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhM/hjubah}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh]h)}(hskb->vlan_protoh]hskb->vlan_proto}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhM/hjubah}(h]h ]h"]h$]h&]uh1jhjubeh}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh](j)}(hhh]h)}(hrandh]hrand}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhM0hjubah}(h]h ]h"]h$]h&]uh1jhjubj)}(hhh]h)}(hget_random_u32()h]hget_random_u32()}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhM0hjubah}(h]h ]h"]h$]h&]uh1jhjubeh}(h]h ]h"]h$]h&]uh1jhjubeh}(h]h ]h"]h$]h&]uh1jhj3ubeh}(h]h ]h"]h$]h&]colsKuh1jhj0ubah}(h]h ]h"]h$]h&]uh1jhj,ubah}(h]h ]h"]h$]h&]uh1jhhhMhjghhubh)}(hKThese extensions can also be prefixed with '#'. Examples for low-level BPF:h]hOThese extensions can also be prefixed with ‘#’. Examples for low-level BPF:}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhM3hjghhubh)}(h**ARP packets**::h](hstrong)}(h**ARP packets**h]h ARP packets}(hj*hhhNhNubah}(h]h ]h"]h$]h&]uh1j(hj$ubh:}(hj$hhhNhNubeh}(h]h ]h"]h$]h&]uh1hhhhM6hjghhubjJ)}(h.ldh [12] jne #0x806, drop ret #-1 drop: ret #0h]h.ldh [12] jne #0x806, drop ret #-1 drop: ret #0}hjBsbah}(h]h ]h"]h$]h&]hhuh1jIhhhM8hjghhubh)}(h**IPv4 TCP packets**::h](j))}(h**IPv4 TCP packets**h]hIPv4 TCP packets}(hjThhhNhNubah}(h]h ]h"]h$]h&]uh1j(hjPubh:}(hjPhhhNhNubeh}(h]h ]h"]h$]h&]uh1hhhhM=hjghhubjJ)}(hEldh [12] jne #0x800, drop ldb [23] jneq #6, drop ret #-1 drop: ret #0h]hEldh [12] jne #0x800, drop ldb [23] jneq #6, drop ret #-1 drop: ret #0}hjlsbah}(h]h ]h"]h$]h&]hhuh1jIhhhM?hjghhubh)}(h)**icmp random packet sampling, 1 in 4**::h](j))}(h'**icmp random packet sampling, 1 in 4**h]h#icmp random packet sampling, 1 in 4}(hj~hhhNhNubah}(h]h ]h"]h$]h&]uh1j(hjzubh:}(hjzhhhNhNubeh}(h]h ]h"]h$]h&]uh1hhhhMFhjghhubjJ)}(hldh [12] jne #0x800, drop ldb [23] jneq #1, drop # get a random uint32 number ld rand mod #4 jneq #1, drop ret #-1 drop: ret #0h]hldh [12] jne #0x800, drop ldb [23] jneq #1, drop # get a random uint32 number ld rand mod #4 jneq #1, drop ret #-1 drop: ret #0}hjsbah}(h]h ]h"]h$]h&]hhuh1jIhhhMHhjghhubh)}(h**SECCOMP filter example**::h](j))}(h**SECCOMP filter example**h]hSECCOMP filter example}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1j(hjubh:}(hjhhhNhNubeh}(h]h ]h"]h$]h&]uh1hhhhMShjghhubjJ)}(hXld [4] /* offsetof(struct seccomp_data, arch) */ jne #0xc000003e, bad /* AUDIT_ARCH_X86_64 */ ld [0] /* offsetof(struct seccomp_data, nr) */ jeq #15, good /* __NR_rt_sigreturn */ jeq #231, good /* __NR_exit_group */ jeq #60, good /* __NR_exit */ jeq #0, good /* __NR_read */ jeq #1, good /* __NR_write */ jeq #5, good /* __NR_fstat */ jeq #9, good /* __NR_mmap */ jeq #14, good /* __NR_rt_sigprocmask */ jeq #13, good /* __NR_rt_sigaction */ jeq #35, good /* __NR_nanosleep */ bad: ret #0 /* SECCOMP_RET_KILL_THREAD */ good: ret #0x7fff0000 /* SECCOMP_RET_ALLOW */h]hXld [4] /* offsetof(struct seccomp_data, arch) */ jne #0xc000003e, bad /* AUDIT_ARCH_X86_64 */ ld [0] /* offsetof(struct seccomp_data, nr) */ jeq #15, good /* __NR_rt_sigreturn */ jeq #231, good /* __NR_exit_group */ jeq #60, good /* __NR_exit */ jeq #0, good /* __NR_read */ jeq #1, good /* __NR_write */ jeq #5, good /* __NR_fstat */ jeq #9, good /* __NR_mmap */ jeq #14, good /* __NR_rt_sigprocmask */ jeq #13, good /* __NR_rt_sigaction */ jeq #35, good /* __NR_nanosleep */ bad: ret #0 /* SECCOMP_RET_KILL_THREAD */ good: ret #0x7fff0000 /* SECCOMP_RET_ALLOW */}hjsbah}(h]h ]h"]h$]h&]hhuh1jIhhhMUhjghhubh)}(h%Examples for low-level BPF extension:h]h%Examples for low-level BPF extension:}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhMehjghhubh)}(h#**Packet for interface index 13**::h](j))}(h!**Packet for interface index 13**h]hPacket for interface index 13}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1j(hjubh:}(hjhhhNhNubeh}(h]h ]h"]h$]h&]uh1hhhhMghjghhubjJ)}(h,ld ifidx jneq #13, drop ret #-1 drop: ret #0h]h,ld ifidx jneq #13, drop ret #-1 drop: ret #0}hjsbah}(h]h ]h"]h$]h&]hhuh1jIhhhMihjghhubh)}(h!**(Accelerated) VLAN w/ id 10**::h](j))}(h**(Accelerated) VLAN w/ id 10**h]h(Accelerated) VLAN w/ id 10}(hj hhhNhNubah}(h]h ]h"]h$]h&]uh1j(hjubh:}(hjhhhNhNubeh}(h]h ]h"]h$]h&]uh1hhhhMnhjghhubjJ)}(h/ld vlan_tci jneq #10, drop ret #-1 drop: ret #0h]h/ld vlan_tci jneq #10, drop ret #-1 drop: ret #0}hj"sbah}(h]h ]h"]h$]h&]hhuh1jIhhhMphjghhubh)}(hMThe ARP filter shown above corresponds to the following sock_filter entries::h]hLThe ARP filter shown above corresponds to the following sock_filter entries:}(hj0hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhMuhjghhubjJ)}(hw{ 0x28, 0, 0, 0x0000000c }, { 0x15, 0, 1, 0x00000806 }, { 0x06, 0, 0, 0xffffffff }, { 0x06, 0, 0, 0000000000 },h]hw{ 0x28, 0, 0, 0x0000000c }, { 0x15, 0, 1, 0x00000806 }, { 0x06, 0, 0, 0xffffffff }, { 0x06, 0, 0, 0000000000 },}hj>sbah}(h]h ]h"]h$]h&]hhuh1jIhhhMxhjghhubeh}(h]bpf-engine-and-instruction-setah ]h"]bpf engine and instruction setah$]h&]uh1hhhhhhhhKubh)}(hhh](h)}(h JIT compilerh]h JIT compiler}(hjWhhhNhNubah}(h]h ]h"]h$]h&]uh1hhjThhhhhM~ubh)}(hX;The Linux kernel has a built-in BPF JIT compiler for x86_64, SPARC, PowerPC, ARM, ARM64, MIPS, RISC-V, s390, and ARC and can be enabled through CONFIG_BPF_JIT. The JIT compiler is transparently invoked for each attached filter from user space or for internal kernel users if it has been previously enabled by root::h]hX:The Linux kernel has a built-in BPF JIT compiler for x86_64, SPARC, PowerPC, ARM, ARM64, MIPS, RISC-V, s390, and ARC and can be enabled through CONFIG_BPF_JIT. The JIT compiler is transparently invoked for each attached filter from user space or for internal kernel users if it has been previously enabled by root:}(hjehhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhMhjThhubjJ)}(h*echo 1 > /proc/sys/net/core/bpf_jit_enableh]h*echo 1 > /proc/sys/net/core/bpf_jit_enable}hjssbah}(h]h ]h"]h$]h&]hhuh1jIhhhMhjThhubh)}(hvFor JIT developers, doing audits etc, each compile run can output the generated opcode image into the kernel log via::h]huFor JIT developers, doing audits etc, each compile run can output the generated opcode image into the kernel log via:}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhMhjThhubjJ)}(h*echo 2 > /proc/sys/net/core/bpf_jit_enableh]h*echo 2 > /proc/sys/net/core/bpf_jit_enable}hjsbah}(h]h ]h"]h$]h&]hhuh1jIhhhMhjThhubh)}(hExample output from dmesg::h]hExample output from dmesg:}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhMhjThhubjJ)}(hX[ 3389.935842] flen=6 proglen=70 pass=3 image=ffffffffa0069c8f [ 3389.935847] JIT code: 00000000: 55 48 89 e5 48 83 ec 60 48 89 5d f8 44 8b 4f 68 [ 3389.935849] JIT code: 00000010: 44 2b 4f 6c 4c 8b 87 d8 00 00 00 be 0c 00 00 00 [ 3389.935850] JIT code: 00000020: e8 1d 94 ff e0 3d 00 08 00 00 75 16 be 17 00 00 [ 3389.935851] JIT code: 00000030: 00 e8 28 94 ff e0 83 f8 01 75 07 b8 ff ff 00 00 [ 3389.935852] JIT code: 00000040: eb 02 31 c0 c9 c3h]hX[ 3389.935842] flen=6 proglen=70 pass=3 image=ffffffffa0069c8f [ 3389.935847] JIT code: 00000000: 55 48 89 e5 48 83 ec 60 48 89 5d f8 44 8b 4f 68 [ 3389.935849] JIT code: 00000010: 44 2b 4f 6c 4c 8b 87 d8 00 00 00 be 0c 00 00 00 [ 3389.935850] JIT code: 00000020: e8 1d 94 ff e0 3d 00 08 00 00 75 16 be 17 00 00 [ 3389.935851] JIT code: 00000030: 00 e8 28 94 ff e0 83 f8 01 75 07 b8 ff ff 00 00 [ 3389.935852] JIT code: 00000040: eb 02 31 c0 c9 c3}hjsbah}(h]h ]h"]h$]h&]hhuh1jIhhhMhjThhubh)}(hXvWhen CONFIG_BPF_JIT_ALWAYS_ON is enabled, bpf_jit_enable is permanently set to 1 and setting any other value than that will return in failure. This is even the case for setting bpf_jit_enable to 2, since dumping the final JIT image into the kernel log is discouraged and introspection through bpftool (under tools/bpf/bpftool/) is the generally recommended approach instead.h]hXvWhen CONFIG_BPF_JIT_ALWAYS_ON is enabled, bpf_jit_enable is permanently set to 1 and setting any other value than that will return in failure. This is even the case for setting bpf_jit_enable to 2, since dumping the final JIT image into the kernel log is discouraged and introspection through bpftool (under tools/bpf/bpftool/) is the generally recommended approach instead.}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhMhjThhubeh}(h] jit-compilerah ]h"] jit compilerah$]h&]uh1hhhhhhhhM~ubh)}(hhh](h)}(hBPF kernel internalsh]hBPF kernel internals}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhjhhhhhMubh)}(hXxInternally, for the kernel interpreter, a different instruction set format with similar underlying principles from BPF described in previous paragraphs is being used. However, the instruction set format is modelled closer to the underlying architecture to mimic native instruction sets, so that a better performance can be achieved (more details later). This new ISA is called eBPF. See the ../bpf/index.rst for details. (Note: eBPF which originates from [e]xtended BPF is not the same as BPF extensions! While eBPF is an ISA, BPF extensions date back to classic BPF's 'overloading' of BPF_LD | BPF_{B,H,W} | BPF_ABS instruction.)h]hX~Internally, for the kernel interpreter, a different instruction set format with similar underlying principles from BPF described in previous paragraphs is being used. However, the instruction set format is modelled closer to the underlying architecture to mimic native instruction sets, so that a better performance can be achieved (more details later). This new ISA is called eBPF. See the ../bpf/index.rst for details. (Note: eBPF which originates from [e]xtended BPF is not the same as BPF extensions! While eBPF is an ISA, BPF extensions date back to classic BPF’s ‘overloading’ of BPF_LD | BPF_{B,H,W} | BPF_ABS instruction.)}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhMhjhhubh)}(hX5The new instruction set was originally designed with the possible goal in mind to write programs in "restricted C" and compile into eBPF with a optional GCC/LLVM backend, so that it can just-in-time map to modern 64-bit CPUs with minimal performance overhead over two steps, that is, C -> eBPF -> native code.h]hX9The new instruction set was originally designed with the possible goal in mind to write programs in “restricted C” and compile into eBPF with a optional GCC/LLVM backend, so that it can just-in-time map to modern 64-bit CPUs with minimal performance overhead over two steps, that is, C -> eBPF -> native code.}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhMhjhhubh)}(hXCurrently, the new format is being used for running user BPF programs, which includes seccomp BPF, classic socket filters, cls_bpf traffic classifier, team driver's classifier for its load-balancing mode, netfilter's xt_bpf extension, PTP dissector/classifier, and much more. They are all internally converted by the kernel into the new instruction set representation and run in the eBPF interpreter. For in-kernel handlers, this all works transparently by using bpf_prog_create() for setting up the filter, resp. bpf_prog_destroy() for destroying it. The function bpf_prog_run(filter, ctx) transparently invokes eBPF interpreter or JITed code to run the filter. 'filter' is a pointer to struct bpf_prog that we got from bpf_prog_create(), and 'ctx' the given context (e.g. skb pointer). All constraints and restrictions from bpf_check_classic() apply before a conversion to the new layout is being done behind the scenes!h]hXCurrently, the new format is being used for running user BPF programs, which includes seccomp BPF, classic socket filters, cls_bpf traffic classifier, team driver’s classifier for its load-balancing mode, netfilter’s xt_bpf extension, PTP dissector/classifier, and much more. They are all internally converted by the kernel into the new instruction set representation and run in the eBPF interpreter. For in-kernel handlers, this all works transparently by using bpf_prog_create() for setting up the filter, resp. bpf_prog_destroy() for destroying it. The function bpf_prog_run(filter, ctx) transparently invokes eBPF interpreter or JITed code to run the filter. ‘filter’ is a pointer to struct bpf_prog that we got from bpf_prog_create(), and ‘ctx’ the given context (e.g. skb pointer). All constraints and restrictions from bpf_check_classic() apply before a conversion to the new layout is being done behind the scenes!}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhMhjhhubh)}(hCurrently, the classic BPF format is being used for JITing on most 32-bit architectures, whereas x86-64, aarch64, s390x, powerpc64, sparc64, arm32, riscv64, riscv32, loongarch64, arc perform JIT compilation from eBPF instruction set.h]hCurrently, the classic BPF format is being used for JITing on most 32-bit architectures, whereas x86-64, aarch64, s390x, powerpc64, sparc64, arm32, riscv64, riscv32, loongarch64, arc perform JIT compilation from eBPF instruction set.}(hj hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhMhjhhubeh}(h]bpf-kernel-internalsah ]h"]bpf kernel internalsah$]h&]uh1hhhhhhhhMubh)}(hhh](h)}(hTestingh]hTesting}(hj#hhhNhNubah}(h]h ]h"]h$]h&]uh1hhj hhhhhMubh)}(hXQThe BPF selftests under tools/testing/selftests/bpf ship instruction tests in test_progs, see jit_insns, which runs the eBPF instructions over a range of operand magnitudes and signs, register combinations, memory offsets and jump offsets against the BPF interpreter or the JIT compiler, depending on the net.core.bpf_jit_enable setting.h]hXQThe BPF selftests under tools/testing/selftests/bpf ship instruction tests in test_progs, see jit_insns, which runs the eBPF instructions over a range of operand magnitudes and signs, register combinations, memory offsets and jump offsets against the BPF interpreter or the JIT compiler, depending on the net.core.bpf_jit_enable setting.}(hj1hhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhMhj hhubeh}(h]testingah ]h"]testingah$]h&]uh1hhhhhhhhMubh)}(hhh](h)}(hMisch]hMisc}(hjJhhhNhNubah}(h]h ]h"]h$]h&]uh1hhjGhhhhhMubh)}(hdAlso trinity, the Linux syscall fuzzer, has built-in support for BPF and SECCOMP-BPF kernel fuzzing.h]hdAlso trinity, the Linux syscall fuzzer, has built-in support for BPF and SECCOMP-BPF kernel fuzzing.}(hjXhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhMhjGhhubeh}(h]miscah ]h"]miscah$]h&]uh1hhhhhhhhMubh)}(hhh](h)}(h Written byh]h Written by}(hjqhhhNhNubah}(h]h ]h"]h$]h&]uh1hhjnhhhhhMubh)}(hThe document was written in the hope that it is found useful and in order to give potential BPF hackers or security auditors a better overview of the underlying architecture.h]hThe document was written in the hope that it is found useful and in order to give potential BPF hackers or security auditors a better overview of the underlying architecture.}(hjhhhNhNubah}(h]h ]h"]h$]h&]uh1hhhhMhjnhhubj)}(hhh](j)}(h Jay Schulist h]h)}(hjh](hJay Schulist <}(hjhhhNhNubj)}(hjschlst@samba.orgh]hjschlst@samba.org}(hjhhhNhNubah}(h]h ]h"]h$]h&]refurimailto:jschlst@samba.orguh1jhjubh>}(hjhhhNhNubeh}(h]h ]h"]h$]h&]uh1hhhhMhjubah}(h]h ]h"]h$]h&]uh1jhjhhhhhNubj)}(h&Daniel Borkmann h]h)}(hjh](hDaniel Borkmann <}(hjhhhNhNubj)}(hdaniel@iogearbox.neth]hdaniel@iogearbox.net}(hjhhhNhNubah}(h]h ]h"]h$]h&]refurimailto:daniel@iogearbox.netuh1jhjubh>}(hjhhhNhNubeh}(h]h ]h"]h$]h&]uh1hhhhMhjubah}(h]h ]h"]h$]h&]uh1jhjhhhhhNubj)}(h#Alexei Starovoitov h]h)}(hjh](hAlexei Starovoitov <}(hjhhhNhNubj)}(hast@kernel.orgh]hast@kernel.org}(hjhhhNhNubah}(h]h ]h"]h$]h&]refurimailto:ast@kernel.orguh1jhjubh>}(hjhhhNhNubeh}(h]h ]h"]h$]h&]uh1hhhhMhjubah}(h]h ]h"]h$]h&]uh1jhjhhhhhNubeh}(h]h ]h"]h$]h&]j;-uh1jhhhMhjnhhubeh}(h] written-byah ]h"] written byah$]h&]uh1hhhhhhhhMubeh}(h](5linux-socket-filtering-aka-berkeley-packet-filter-bpfheh ]h"](7linux socket filtering aka berkeley packet filter (bpf)networking-filtereh$]h&]uh1hhhhhhhhKexpect_referenced_by_name}j&hsexpect_referenced_by_id}hhsubeh}(h]h ]h"]h$]h&]sourcehuh1hcurrent_sourceN current_lineNsettingsdocutils.frontendValues)}(hN generatorN datestampN source_linkN source_urlN toc_backlinksjfootnote_backlinksK sectnum_xformKstrip_commentsNstrip_elements_with_classesN strip_classesN report_levelK halt_levelKexit_status_levelKdebugNwarning_streamN tracebackinput_encoding 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image_loadinglinkembed_stylesheetcloak_email_addressessection_self_linkenvNubreporterNindirect_targets]substitution_defs}substitution_names}refnames}1]jasrefids}h]hasnameids}(j&hj%j"jjj'j$jjjjjdjajQjNjjjjjDjAjkjhjju nametypes}(j&j%jj'jjjdjQjjjDjkjuh}(hhj"hjhj$jjjjjjj*jajjNjgjjTjjjAj jhjGjjnu footnote_refs}j]jas citation_refs} autofootnotes]autofootnote_refs]symbol_footnotes]symbol_footnote_refs] footnotes]ja citations]autofootnote_startKsymbol_footnote_startK id_counter collectionsCounter}j]KsRparse_messages]transform_messages]hsystem_message)}(hhh]h)}(hhh]h7Hyperlink target "networking-filter" is not referenced.}hjsbah}(h]h ]h"]h$]h&]uh1hhjubah}(h]h ]h"]h$]h&]levelKtypeINFOsourcehnjlineKuh1juba transformerN include_log] decorationNhhub.