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Don't overwrite original IP header for Echo reply

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...to avoid data races with other goroutines that may read from the same
byte slice. This can occur when a packet is delivered to a raw or packet
endpoint and we modify the IP header (to send the reply) at the the same
time when another goroutine handles a read operation for a raw or packet
endpoint.

PiperOrigin-RevId: 418534467
This commit is contained in:
Ghanan Gowripalan
2021-12-27 15:45:04 -08:00
committed by gVisor bot
parent 9c9fdfa075
commit e739f982c0
1 changed files with 8 additions and 5 deletions
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pkg/tcpip/network/ipv4/icmp.go
+8 -5
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@@ -262,11 +262,6 @@ func (e *endpoint) handleICMP(pkt *stack.PacketBuffer) {
return
}
// Take the base of the incoming request IP header but replace the options.
replyHeaderLength := uint8(header.IPv4MinimumSize + len(newOptions))
replyIPHdr := header.IPv4(append(iph[:header.IPv4MinimumSize:header.IPv4MinimumSize], newOptions...))
replyIPHdr.SetHeaderLength(replyHeaderLength)
// As per RFC 1122 section 3.2.1.3, when a host sends any datagram, the IP
// source address MUST be one of its own IP addresses (but not a broadcast
// or multicast address).
@@ -313,6 +308,14 @@ func (e *endpoint) handleICMP(pkt *stack.PacketBuffer) {
// We need to produce the entire packet in the data segment in order to
// use WriteHeaderIncludedPacket(). WriteHeaderIncludedPacket sets the
// total length and the header checksum so we don't need to set those here.
//
// Take the base of the incoming request IP header but replace the options.
replyHeaderLength := uint8(header.IPv4MinimumSize + len(newOptions))
replyIPHdrBytes := make([]byte, 0, replyHeaderLength)
replyIPHdrBytes = append(replyIPHdrBytes, iph[:header.IPv4MinimumSize]...)
replyIPHdrBytes = append(replyIPHdrBytes, newOptions...)
replyIPHdr := header.IPv4(replyIPHdrBytes)
replyIPHdr.SetHeaderLength(replyHeaderLength)
replyIPHdr.SetSourceAddress(r.LocalAddress())
replyIPHdr.SetDestinationAddress(r.RemoteAddress())
replyIPHdr.SetTTL(r.DefaultTTL())