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net, wgengine/capture: encode NAT addresses in pcap stream

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Signed-off-by: Tom DNetto <tom@tailscale.com>
This commit is contained in:
Tom DNetto
2023-03-30 12:39:39 -07:00
committed by Tom
parent 92459a9248
commit 6a627e5a33
7 changed files with 94 additions and 28 deletions
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17
net/packet/packet.go
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@ -34,6 +34,14 @@ const (
TCPECNBits TCPFlag = TCPECNEcho | TCPCWR
)
// CaptureMeta contains metadata that is used when debugging.
type CaptureMeta struct {
DidSNAT bool // SNAT was performed & the address was updated.
OriginalSrc netip.AddrPort // The source address before SNAT was performed.
DidDNAT bool // DNAT was performed & the address was updated.
OriginalDst netip.AddrPort // The destination address before DNAT was performed.
}
// Parsed is a minimal decoding of a packet suitable for use in filters.
type Parsed struct {
// b is the byte buffer that this decodes.
@ -58,6 +66,9 @@ type Parsed struct {
Dst netip.AddrPort
// TCPFlags is the packet's TCP flag bits. Valid iff IPProto == TCP.
TCPFlags TCPFlag
// CaptureMeta contains metadata that is used when debugging.
CaptureMeta CaptureMeta
}
func (p *Parsed) String() string {
@ -84,6 +95,7 @@ func (p *Parsed) String() string {
// and shouldn't need any memory allocation.
func (q *Parsed) Decode(b []byte) {
q.b = b
q.CaptureMeta = CaptureMeta{} // Clear any capture metadata if it exists.
if len(b) < 1 {
q.IPVersion = 0
@ -447,6 +459,8 @@ func (q *Parsed) UpdateSrcAddr(src netip.Addr) {
if q.IPVersion != 4 || src.Is6() {
panic("UpdateSrcAddr: only IPv4 is supported")
}
q.CaptureMeta.DidSNAT = true
q.CaptureMeta.OriginalSrc = q.Src
old := q.Src.Addr()
q.Src = netip.AddrPortFrom(src, q.Src.Port())
@ -465,6 +479,9 @@ func (q *Parsed) UpdateDstAddr(dst netip.Addr) {
panic("UpdateDstAddr: only IPv4 is supported")
}
q.CaptureMeta.DidDNAT = true
q.CaptureMeta.OriginalDst = q.Dst
old := q.Dst.Addr()
q.Dst = netip.AddrPortFrom(dst, q.Dst.Port())