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// Copyright 2011 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.

// Linux socket filter

package syscall

import (
        "unsafe"
)

func LsfStmt(code, k int) *SockFilter {
        return &SockFilter{Code: uint16(code), K: uint32(k)}
}

func LsfJump(code, k, jt, jf int) *SockFilter {
        return &SockFilter{Code: uint16(code), Jt: uint8(jt), Jf: uint8(jf), K: uint32(k)}
}

func LsfSocket(ifindex, proto int) (int, error) {
        var lsall SockaddrLinklayer
        s, e := Socket(AF_PACKET, SOCK_RAW, proto)
        if e != nil {
                return 0, e
        }
        p := (*[2]byte)(unsafe.Pointer(&lsall.Protocol))
        p[0] = byte(proto >> 8)
        p[1] = byte(proto)
        lsall.Ifindex = ifindex
        e = Bind(s, &lsall)
        if e != nil {
                Close(s)
                return 0, e
        }
        return s, nil
}

type iflags struct {
        name  [IFNAMSIZ]byte
        flags uint16
}

func SetLsfPromisc(name string, m bool) error {
        s, e := Socket(AF_INET, SOCK_DGRAM, 0)
        if e != nil {
                return e
        }
        defer Close(s)
        var ifl iflags
        copy(ifl.name[:], []byte(name))
        _, _, ep := Syscall(SYS_IOCTL, uintptr(s), SIOCGIFFLAGS, uintptr(unsafe.Pointer(&ifl)))
        if ep != 0 {
                return Errno(ep)
        }
        if m {
                ifl.flags |= uint16(IFF_PROMISC)
        } else {
                ifl.flags &= ^uint16(IFF_PROMISC)
        }
        _, _, ep = Syscall(SYS_IOCTL, uintptr(s), SIOCSIFFLAGS, uintptr(unsafe.Pointer(&ifl)))
        if ep != 0 {
                return Errno(ep)
        }
        return nil
}

func AttachLsf(fd int, i []SockFilter) error {
        var p SockFprog
        p.Len = uint16(len(i))
        p.Filter = (*SockFilter)(unsafe.Pointer(&i[0]))
        return setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, uintptr(unsafe.Pointer(&p)), unsafe.Sizeof(p))
}

func DetachLsf(fd int) error {
        var dummy int
        return setsockopt(fd, SOL_SOCKET, SO_DETACH_FILTER, uintptr(unsafe.Pointer(&dummy)), unsafe.Sizeof(dummy))
}