From 14bb08c1df8db9ec6c8a05520d4eee67971235d9 Mon Sep 17 00:00:00 2001 From: Dimitri Sokolyuk Date: Thu, 27 Sep 2018 20:03:23 +0200 Subject: mod tidy --- vendor/golang.org/x/net/bpf/doc.go | 82 -------------------------------------- 1 file changed, 82 deletions(-) delete mode 100644 vendor/golang.org/x/net/bpf/doc.go (limited to 'vendor/golang.org/x/net/bpf/doc.go') diff --git a/vendor/golang.org/x/net/bpf/doc.go b/vendor/golang.org/x/net/bpf/doc.go deleted file mode 100644 index ae62feb..0000000 --- a/vendor/golang.org/x/net/bpf/doc.go +++ /dev/null @@ -1,82 +0,0 @@ -// Copyright 2016 The Go Authors. All rights reserved. -// Use of this source code is governed by a BSD-style -// license that can be found in the LICENSE file. - -/* - -Package bpf implements marshaling and unmarshaling of programs for the -Berkeley Packet Filter virtual machine, and provides a Go implementation -of the virtual machine. - -BPF's main use is to specify a packet filter for network taps, so that -the kernel doesn't have to expensively copy every packet it sees to -userspace. However, it's been repurposed to other areas where running -user code in-kernel is needed. For example, Linux's seccomp uses BPF -to apply security policies to system calls. For simplicity, this -documentation refers only to packets, but other uses of BPF have their -own data payloads. - -BPF programs run in a restricted virtual machine. It has almost no -access to kernel functions, and while conditional branches are -allowed, they can only jump forwards, to guarantee that there are no -infinite loops. - -The virtual machine - -The BPF VM is an accumulator machine. Its main register, called -register A, is an implicit source and destination in all arithmetic -and logic operations. The machine also has 16 scratch registers for -temporary storage, and an indirection register (register X) for -indirect memory access. All registers are 32 bits wide. - -Each run of a BPF program is given one packet, which is placed in the -VM's read-only "main memory". LoadAbsolute and LoadIndirect -instructions can fetch up to 32 bits at a time into register A for -examination. - -The goal of a BPF program is to produce and return a verdict (uint32), -which tells the kernel what to do with the packet. In the context of -packet filtering, the returned value is the number of bytes of the -packet to forward to userspace, or 0 to ignore the packet. Other -contexts like seccomp define their own return values. - -In order to simplify programs, attempts to read past the end of the -packet terminate the program execution with a verdict of 0 (ignore -packet). This means that the vast majority of BPF programs don't need -to do any explicit bounds checking. - -In addition to the bytes of the packet, some BPF programs have access -to extensions, which are essentially calls to kernel utility -functions. Currently, the only extensions supported by this package -are the Linux packet filter extensions. - -Examples - -This packet filter selects all ARP packets. - - bpf.Assemble([]bpf.Instruction{ - // Load "EtherType" field from the ethernet header. - bpf.LoadAbsolute{Off: 12, Size: 2}, - // Skip over the next instruction if EtherType is not ARP. - bpf.JumpIf{Cond: bpf.JumpNotEqual, Val: 0x0806, SkipTrue: 1}, - // Verdict is "send up to 4k of the packet to userspace." - bpf.RetConstant{Val: 4096}, - // Verdict is "ignore packet." - bpf.RetConstant{Val: 0}, - }) - -This packet filter captures a random 1% sample of traffic. - - bpf.Assemble([]bpf.Instruction{ - // Get a 32-bit random number from the Linux kernel. - bpf.LoadExtension{Num: bpf.ExtRand}, - // 1% dice roll? - bpf.JumpIf{Cond: bpf.JumpLessThan, Val: 2^32/100, SkipFalse: 1}, - // Capture. - bpf.RetConstant{Val: 4096}, - // Ignore. - bpf.RetConstant{Val: 0}, - }) - -*/ -package bpf // import "golang.org/x/net/bpf" -- cgit v1.2.3