From 9ea8663420e2b591ff7e43176fbfb2137aacf79c Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Sun, 5 May 2013 13:15:10 +0200 Subject: misc: move file to source root Only have Makefile specific folders in the project root where the binaries are stored, the rest should be part of the repository root. Signed-off-by: Daniel Borkmann --- man/bpfc.8 | 320 ------------------------------------------------------------- 1 file changed, 320 deletions(-) delete mode 100644 man/bpfc.8 (limited to 'man/bpfc.8') diff --git a/man/bpfc.8 b/man/bpfc.8 deleted file mode 100644 index 622014c..0000000 --- a/man/bpfc.8 +++ /dev/null @@ -1,320 +0,0 @@ -.\" netsniff-ng - the packet sniffing beast -.\" Copyright 2013 Daniel Borkmann. -.\" Subject to the GPL, version 2. - -.TH BPFC 8 "03 March 2013" "Linux" "netsniff-ng toolkit" -.SH NAME -bpfc \- a Berkeley Packet Filter assembler/compiler - -.SH SYNOPSIS - -\fB bpfc\fR { [\fIoptions\fR] | [\fIsource-file\fR] } - -.SH DESCRIPTION - -bpfc is a small Berkeley Packet Filter assembler/compiler which is able to -translate BPF assembler-like mnemonics into a numerical or C-like format, -that can be read by tools such as netsniff-ng, iptables (xt_bpf) and many -others. BPF is the one and only upstream filtering construct that is used -in combination with packet(7) sockets. The Linux kernel and also BSD kernels -implement ``virtual machine'' like constructs and JIT compilers that mimic -a small register-based machine in BPF architecture and execute filter code -that is e.g. composed by bpfc on a data buffer that is given by network -packets. The purpose of this is to shift computation in time, so that the -kernel can drop (or truncate) incoming packets as early as possible without -having to push them to user space for further analysis first. Meanwhile, -BPF constructs also find application in other areas like the communication -between user and kernel space. - -By the time of writing this man page, the only available BPF compiler is -part of the pcap(3) library and accessible through a high-level filter -language that might be familiar for many people as tcpdump-like filters. - -However, quite often, it is useful to bypass that compiler and write -optimized code that couldn't be produced by the pcap(3) compiler, was -wrongly optimized, or is defective on purpose in order to debug test kernel -code. Also, a reason to use bpfc could be to try out some new BPF extensions -that are not supported by other compilers. Furthermore, bpfc can be of good -use to verify JIT compiler behaviour or to find possible bugs that need -to be fixed. - -bpfc is implemented with the help of flex(1) and bison(1), tokenizes the -source file in a first stage and parses it's content into an AST. In two -code generation stages it emits target opcodes. bpfc furthermore supports -Linux kernel BPF extensions. More about that can be found in the syntax -section. - -The Linux kernel BPF JIT compiler is automatically turned on if detected -by netsniff-ng. However, it can also be manually turned on through the -command ``echo "1" > /proc/sys/net/core/bpf_jit_enable'' (normal working -mode) or ``echo "2" > /proc/sys/net/core/bpf_jit_enable'' (debug mode -where emitted opcodes of the image are printed to the kernel log). An -architecture generic BPF JIT image disassembler can be found in the kernel -source tree under: tools/net/bpf_jit_disasm.c - -.SH OPTIONS - -.SS -i , --input -Read BPF assembly instruction from an input file or from stdin. - -.SS -f , --format -Specify a different output format than the default that is netsniff-ng -compatible. The specifier can be: C, netsniff-ng, xt_bpf, tcpdump. - -.SS -b, --bypass -Bypass basic filter validation when emitting opcodes. This can be useful -for explicitly creating malformed BPF expressions that should be injected -into the kernel, e.g. for bug testing. - -.SS -V, --verbose -Be more verbose and display some bpfc debugging information. - -.SS -d, --dump -Dump all supported instructions to stdout. - -.SS -v, --version -Show versioning information. - -.SS -h, --help -Show user help. - -.SH SYNTAX - -The BPF architecture resp. register machine consists of the following -elements: - - 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 - -A program, that is translated by bpfc into ``opcodes'' is an array that -consists of the following elements: - - o:16, jt:8, jf:8, k:32 - -The element o 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 -``true'', one for condition ``false''. Last but not least the 32 bit wide -element k contains a miscellaneous argument that can be interpreted in -different ways depending on the given instruction resp. opcode. - -The instruction set consists of load, store, branch, alu, miscellaneous -and return instructions that are also represented in bpfc syntax. This -table also includes own bpfc extensions. All operations are based on -unsigned data structures: - - Instruction Addressing mode Description - - ld 1, 2, 3, 4, 10 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, 10 Load word into X - ldxi 4 Load word into X - ldxb 5 Load byte into X - - st 3 Copy A into M[] - stx 3 Copy X into M[] - - jmp 6 Jump to label - ja 6 Jump to label - jeq 7, 8 Jump on k == A - jneq 8 Jump on k != A - jne 8 Jump on k != A - jlt 8 Jump on k < A - jle 8 Jump on k <= A - jgt 7, 8 Jump on k > A - jge 7, 8 Jump on k >= A - jset 7, 8 Jump on k & A - - add 0, 4 A + - sub 0, 4 A - - mul 0, 4 A * - div 0, 4 A / - mod 0, 4 A % - neg 0, 4 !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, 9 Return - - Addressing mode Syntax Description - - 0 x Register X - 1 [k] BHW at byte offset k in the packet - 2 [x + k] BHW at the offset X + k in the packet - 3 M[k] Word at offset k in M[] - 4 #k Literal value stored in k - 5 4*([k]&0xf) Lower nibble * 4 at byte offset k in the packet - 6 L Jump label L - 7 #k,Lt,Lf Jump to Lt if true, otherwise jump to Lf - 8 #k,Lt Jump to Lt if predicate is true - 9 a Accumulator A - 10 extension BPF extension (see next table) - - Extension (and alias) Description - - #len, len, #pktlen, pktlen Length of packet (skb->len) - #pto, pto, #proto, proto Ethernet type field (skb->protocol) - #type, type Packet type (**) (skb->pkt_type) - #poff, poff Detected payload start offset - #ifx, ifx, #ifidx, ifidx Interface index (skb->dev->ifindex) - #nla, nla Netlink attribute of type X with offset A - #nlan, nlan Nested Netlink attribute of type X with offset A - #mark, mark Packet mark (skb->mark) - #que, que, #queue, queue, #Q, Q NIC queue index (skb->queue_mapping) - #hat, hat, #hatype, hatype NIC hardware type (**) (skb->dev->type) - #rxh, rxh, #rxhash, rxhash Receive hash (skb->rxhash) - #cpu, cpu Current CPU (raw_smp_processor_id()) - #vlant, vlant, #vlan_tci, vlan_tci VLAN TCI value (vlan_tx_tag_get(skb)) - #vlanp, vlanp VLAN present (vlan_tx_tag_present(skb)) - - Further extension details (**) Value - - #type, type 0 - to us / host - 1 - to all / broadcast - 2 - to group / multicast - 3 - to others (promiscuous mode) - 4 - outgoing of any type - - #hat, hat, #hatype, hatype 1 - Ethernet 10Mbps - 8 - APPLEtalk - 19 - ATM - 24 - IEEE 1394 IPv4 - RFC 2734 - 32 - InfiniBand - 768 - IPIP tunnel - 769 - IP6IP6 tunnel - 772 - Loopback device - 778 - GRE over IP - 783 - Linux-IrDA - 801 - IEEE 802.11 - 802 - IEEE 802.11 + Prism2 header - 803 - IEEE 802.11 + radiotap header - 823 - GRE over IP6 - [...] See include/uapi/linux/if_arp.h - -Note that the majority of BPF extensions are available on Linux only. - -There are two types of comments in bpfc source-files: - - 1. Multi-line C-style comments: /* put comment here */ - 2. Single-line ASM-style comments: ; put comment here - -Used Abbreviations: - - BHW: byte, half-word, or word - -.SH SOURCE EXAMPLES - -In this section, we give a couple of examples for bpfc source-files, in other -words, some small example filter programs: - -.SS Only return packet headers (truncate packets): - - ld poff - ret a - -.SS Only allow ARP packets: - - ldh [12] - jne #0x806, drop - ret #-1 - drop: ret #0 - -.SS Only allow IPv4 TCP packets: - - ldh [12] - jne #0x800, drop - ldb [23] - jneq #6, drop - ret #-1 - drop: ret #0 - -.SS Only allow IPv4 TCP, SSH traffic: - - ldh [12] - jne #0x800, drop - ldb [23] - jneq #6, drop - ldh [20] - jset #0x1fff, drop - ldxb 4 * ([14] & 0xf) - ldh [x + 14] - jeq #0x16, pass - ldh [x + 16] - jne #0x16, drop - pass: ret #-1 - drop: ret #0 - -.SS Allow any (hardware accelerated) VLAN: - - ld vlanp - jeq #0, drop - ret #-1 - drop: ret #0 - -.SS Only allow traffic for (hardware accelerated) VLAN 10: - - ld vlant - jneq #10, drop - ret #-1 - drop: ret #0 - -.SS More pedantic check for the above VLAN example: - - ld vlanp - jeq #0, drop - ld vlant - jneq #10, drop - ret #-1 - drop: ret #0 - -.SH USAGE EXAMPLE - -.SS bpfc fubar -Compile the source file ``fubar'' into BPF opcodes. Opcodes will be -directed to stdout. - -.SS bpfc -f xt_bpf -b -i fubar, resp. iptables -A INPUT -m bpf --bytecode "`bpfc -f xt_bpf -i fubar`" -j LOG -Compile the source file ``fubar'' into BPF opcodes, bypass basic filter -validation and emit opcodes in netfilter's xt_bpf readable format. - -.SS bpfc - -Read bpfc instruction from stdin and emit opcodes to stdout. - -.SS bpfc foo > bar, resp. netsniff-ng -f bar ... -Compile filter instructions from file foo and redirect bpfc's output into -the file bar, that can then be read by netsniff-ng(8) through option -f. - -.SS bpfc -f tcpdump -i fubar -Output opcodes from source file fubar in the same behaviour as ``tcpdump -ddd''. - -.SH LEGAL -bpfc is licensed under the GNU GPL version 2.0. - -.SH HISTORY -.B bpfc -was originally written for the netsniff-ng toolkit by Daniel Borkmann. It -is currently maintained by Tobias Klauser and Daniel -Borkmann . - -.SH SEE ALSO -.BR netsniff-ng (8), -.BR trafgen (8), -.BR mausezahn (8), -.BR ifpps (8), -.BR flowtop (8), -.BR astraceroute (8), -.BR curvetun (8) - -.SH AUTHOR -Manpage was written by Daniel Borkmann. -- cgit v1.2.3-54-g00ecf