/
rawsockrecv.go
196 lines (152 loc) · 3.82 KB
/
rawsockrecv.go
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package rawsockrecv
import (
"fmt"
"net"
"net/netip"
"sync"
"github.com/google/gopacket"
"github.com/google/gopacket/afpacket"
"github.com/google/gopacket/layers"
"github.com/miscord-dev/tetrapod/pkg/hijack/receiver"
"github.com/miscord-dev/tetrapod/pkg/sets"
"github.com/miscord-dev/tetrapod/pkg/sliceutil"
"github.com/miscord-dev/tetrapod/pkg/syncpool"
"golang.org/x/net/bpf"
)
//go:generate go run github.com/cilium/ebpf/cmd/bpf2go -cc $BPF_CLANG -cflags $BPF_CFLAGS -strip $BPF_STRIP -type event bpf bpf.c -- -I/usr/include/x86_64-linux-gnu -Ilinux-5.18.14/tools/lib -Ixdp-tools/headers
func New(port int) (receiver.Receiver, error) {
tPacket, err := afpacket.NewTPacket()
if err != nil {
return nil, fmt.Errorf("failed to init AF_PACKET: %w", err)
}
pool := syncpool.NewPool[message]()
pool.New = func() message {
return message{}
}
rawInstructions, err := bpf.Assemble(generateInstructions(port))
if err != nil {
return nil, fmt.Errorf("failed to assemble instructions: %w", err)
}
if err := tPacket.SetBPF(rawInstructions); err != nil {
return nil, fmt.Errorf("setting bpf failed: %w", err)
}
rr := &rawsockReceiver{
tPacket: tPacket,
ch: make(chan message, 10),
pool: pool,
closed: make(chan struct{}),
}
if err := rr.Refresh(); err != nil {
return nil, fmt.Errorf("failed to refresh addresses: %w", err)
}
go rr.run()
return rr, nil
}
type message struct {
src netip.AddrPort
payload [2048]byte
len int
}
type rawsockReceiver struct {
tPacket *afpacket.TPacket
ch chan message
pool *syncpool.Pool[message]
lock sync.RWMutex
addrs sets.Set[netip.Addr]
closed chan struct{}
}
func (r *rawsockReceiver) check(addr netip.Addr) bool {
r.lock.RLock()
defer r.lock.RUnlock()
return r.addrs.Contains(addr)
}
func (r *rawsockReceiver) run() {
var eth layers.Ethernet
var ip4 layers.IPv4
var ip6 layers.IPv6
var udp layers.UDP
var payload gopacket.Payload
parser := gopacket.NewDecodingLayerParser(layers.LayerTypeEthernet, ð, &ip4, &ip6, &udp, &payload)
buf := make([]byte, 2048)
for {
ci, err := r.tPacket.ReadPacketDataTo(buf)
if err != nil {
return
}
if ci.CaptureLength > 2048 {
continue
}
decoded := []gopacket.LayerType{}
err = parser.DecodeLayers(buf[:ci.CaptureLength], &decoded)
if err != nil {
continue
}
isIPv4 := false
isIPv6 := false
for _, typ := range decoded {
switch typ {
case layers.LayerTypeIPv4:
isIPv4 = true
case layers.LayerTypeIPv6:
isIPv6 = true
}
}
if !isIPv4 && !isIPv6 {
continue
}
var srcIP netip.Addr
var dstIP netip.Addr
if isIPv4 {
srcIP, _ = netip.AddrFromSlice(ip4.SrcIP)
dstIP, _ = netip.AddrFromSlice(ip4.DstIP)
} else {
srcIP, _ = netip.AddrFromSlice(ip6.SrcIP)
dstIP, _ = netip.AddrFromSlice(ip6.DstIP)
}
if !r.check(dstIP) {
continue
}
msg := r.pool.Get()
msg.src = netip.AddrPortFrom(srcIP, uint16(udp.SrcPort))
copy(msg.payload[:], payload.Payload())
msg.len = len(payload.Payload())
select {
case r.ch <- msg:
default:
}
}
}
func (r *rawsockReceiver) Recv(b []byte) (len int, src netip.AddrPort, err error) {
var msg message
select {
case <-r.closed:
return 0, netip.AddrPort{}, net.ErrClosed
case msg = <-r.ch:
}
defer r.pool.Put(msg)
copy(b, msg.payload[:msg.len])
return msg.len, msg.src, nil
}
func (r *rawsockReceiver) Refresh() error {
netAddrs, err := net.InterfaceAddrs()
if err != nil {
return fmt.Errorf("failed to get interface addrs: %w", err)
}
addrs := sets.FromSlice(sliceutil.Map(netAddrs, func(v net.Addr) netip.Addr {
ipNet := v.(*net.IPNet)
c, _ := netip.AddrFromSlice(ipNet.IP)
return c.Unmap()
}))
r.lock.Lock()
r.addrs = addrs
r.lock.Unlock()
return nil
}
func (r *rawsockReceiver) Close() error {
defer func() {
recover()
}()
close(r.closed)
r.tPacket.Close()
return nil
}