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net/packet: add checksum update tests

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Updates tailscale/corp#8020

Signed-off-by: Maisem Ali <maisem@tailscale.com>
This commit is contained in:
Maisem Ali
2023-03-21 15:13:15 -07:00
committed by Maisem Ali
parent 0bf8c8e710
commit 0e203e414f
2 changed files with 74 additions and 3 deletions
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net/packet/packet.go
+7 -3
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@@ -556,14 +556,18 @@ func updateV4PacketChecksums(p *Parsed, old, new netip.Addr) {
// TODO(maisem): more protocols (sctp, gre, dccp)
}
// updateV4Checksum calculates and updates the checksum in the packet buffer
// for a change between old and new. The checksum is updated in place.
// updateV4Checksum calculates and updates the checksum in the packet buffer for
// a change between old and new. The oldSum must point to the 16-bit checksum
// field in the packet buffer that holds the old checksum value, it will be
// updated in place.
//
// The old and new must be the same length, and must be an even number of bytes.
func updateV4Checksum(oldSum, old, new []byte) {
if len(old) != len(new) {
panic("old and new must be the same length")
}
if len(old)%2 != 0 {
panic("old and new must be even length")
panic("old and new must be of even length")
}
/*
RFC 1624