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authorGhanan Gowripalan <ghanan@google.com>2021-01-22 16:03:27 -0800
committergVisor bot <gvisor-bot@google.com>2021-01-22 16:06:05 -0800
commit76da673a0ddaf33e410d48501a9b089979411d4d (patch)
treef21c355eaefefce0e7092f13b5a47cbec2ca8650 /pkg/tcpip/network/ipv4
parentf190e13a74c261176d8619a2fa03fd80a5c74f6d (diff)
Do not modify IGMP packets when verifying checksum
PiperOrigin-RevId: 353336894
Diffstat (limited to 'pkg/tcpip/network/ipv4')
-rw-r--r--pkg/tcpip/network/ipv4/igmp.go15
1 files changed, 7 insertions, 8 deletions
diff --git a/pkg/tcpip/network/ipv4/igmp.go b/pkg/tcpip/network/ipv4/igmp.go
index 9515fde45..4550aacd6 100644
--- a/pkg/tcpip/network/ipv4/igmp.go
+++ b/pkg/tcpip/network/ipv4/igmp.go
@@ -157,14 +157,13 @@ func (igmp *igmpState) handleIGMP(pkt *stack.PacketBuffer) {
}
h := header.IGMP(headerView)
- // Temporarily reset the checksum field to 0 in order to calculate the proper
- // checksum.
- wantChecksum := h.Checksum()
- h.SetChecksum(0)
- gotChecksum := ^header.ChecksumVV(pkt.Data, 0 /* initial */)
- h.SetChecksum(wantChecksum)
-
- if gotChecksum != wantChecksum {
+ // As per RFC 1071 section 1.3,
+ //
+ // To check a checksum, the 1's complement sum is computed over the
+ // same set of octets, including the checksum field. If the result
+ // is all 1 bits (-0 in 1's complement arithmetic), the check
+ // succeeds.
+ if header.ChecksumVV(pkt.Data, 0 /* initial */) != 0xFFFF {
received.checksumErrors.Increment()
return
}