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Add csum_udp4() helper for calculating UDP over IPv4 checksums

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At least two places in passt fill in UDP over IPv4 checksums, although
since UDP checksums are optional with IPv4 that just amounts to storing
a 0 (in tap_ip_send()) or leaving a 0 from an earlier initialization (in
dhcp()).  For consistency, add a helper for this "calculation".

Just for the heck of it, add the option (compile time disabled for now) to
calculate real UDP checksums.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This commit is contained in:
David Gibson
2022-10-19 11:43:47 +11:00
committed by Stefano Brivio
parent 6905ac75ec
commit bd4be308fc
4 changed files with 37 additions and 2 deletions
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2
dhcp.c
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@@ -364,9 +364,9 @@ int dhcp(const struct ctx *c, const struct pool *p)
opt_set_dns_search(c, sizeof(m->o));
uh->len = htons(len = offsetof(struct msg, o) + fill(m) + sizeof(*uh));
uh->check = 0;
uh->source = htons(67);
uh->dest = htons(68);
csum_udp4(uh, c->ip4.gw, c->ip4.addr, uh + 1, len - sizeof(*uh));
iph->tot_len = htons(len += sizeof(*iph));
iph->daddr = c->ip4.addr;