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wgengine/packet: add IPVersion field, don't use IPProto to note version

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As prep for IPv6 log spam fixes in a future change.

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
This commit is contained in:
Brad Fitzpatrick
2020-07-28 16:02:15 -07:00
committed by Brad Fitzpatrick
parent 91d95dafd2
commit 3e3c24b8f6
4 changed files with 70 additions and 49 deletions
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39
wgengine/packet/packet.go
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@ -30,6 +30,8 @@ var (
)
// ParsedPacket is a minimal decoding of a packet suitable for use in filters.
//
// In general, it only supports IPv4. The IPv6 parsing is very minimal.
type ParsedPacket struct {
// b is the byte buffer that this decodes.
b []byte
@ -41,27 +43,32 @@ type ParsedPacket struct {
// This is not the same as len(b) because b can have trailing zeros.
length int
IPProto IPProto // IP subprotocol (UDP, TCP, etc)
SrcIP IP // IP source address
DstIP IP // IP destination address
SrcPort uint16 // TCP/UDP source port
DstPort uint16 // TCP/UDP destination port
TCPFlags uint8 // TCP flags (SYN, ACK, etc)
IPVersion uint8 // 4, 6, or 0
IPProto IPProto // IP subprotocol (UDP, TCP, etc); the NextHeader field for IPv6
SrcIP IP // IP source address (not used for IPv6)
DstIP IP // IP destination address (not used for IPv6)
SrcPort uint16 // TCP/UDP source port
DstPort uint16 // TCP/UDP destination port
TCPFlags uint8 // TCP flags (SYN, ACK, etc)
}
func (q *ParsedPacket) String() string {
switch q.IPProto {
case IPv6:
// NextHeader
type NextHeader uint8
func (p *ParsedPacket) String() string {
if p.IPVersion == 6 {
return "IPv6{???}"
}
switch p.IPProto {
case Unknown:
return "Unknown{???}"
}
sb := strbuilder.Get()
sb.WriteString(q.IPProto.String())
sb.WriteString(p.IPProto.String())
sb.WriteByte('{')
writeIPPort(sb, q.SrcIP, q.SrcPort)
writeIPPort(sb, p.SrcIP, p.SrcPort)
sb.WriteString(" > ")
writeIPPort(sb, q.DstIP, q.DstPort)
writeIPPort(sb, p.DstIP, p.DstPort)
sb.WriteByte('}')
return sb.String()
}
@ -105,20 +112,22 @@ func (q *ParsedPacket) Decode(b []byte) {
q.b = b
if len(b) < ipHeaderLength {
q.IPVersion = 0
q.IPProto = Unknown
return
}
// Check that it's IPv4.
// TODO(apenwarr): consider IPv6 support
switch (b[0] & 0xF0) >> 4 {
q.IPVersion = (b[0] & 0xF0) >> 4
switch q.IPVersion {
case 4:
q.IPProto = IPProto(b[9])
// continue
case 6:
q.IPProto = IPv6
q.IPProto = IPProto(b[6]) // "Next Header" field
return
default:
q.IPVersion = 0
q.IPProto = Unknown
return
}