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nat64: Drop fragmented v4 packets as well as those with options

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In the other direction we also drop packets with options, which covers
fragmented packets.

Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
This commit is contained in:
Toke Høiland-Jørgensen
2021-10-01 00:08:11 +02:00
parent 0c2dd5e5cf
commit 7ec0aabbb0
1 changed files with 10 additions and 3 deletions
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13
nat64-bpf/nat64_kern.c
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@@ -91,10 +91,17 @@ static int nat64_handle_v4(struct __sk_buff *skb, struct hdr_cursor *nh)
*/
ret = TC_ACT_SHOT;
/* we don't bother dealing with IP options or fragmented packets. The
* latter are identified by the 'frag_off' field having a value (either
* the MF bit, or the fragmet offset, or both). However, this field also
* contains the "don't fragment" (DF) bit, which we ignore, so mask that
* out. The DF is the second-most-significant bit (as bit 0 is
* reserved).
*/
iphdr_len = iph->ihl * 4;
/* drop packets with IP options */
if (iphdr_len != sizeof(struct iphdr)) {
DBG("v4: pkt src/dst %pI4/%pI4 has IP options, dropping\n",
if (iphdr_len != sizeof(struct iphdr) ||
(iph->frag_off & ~bpf_htons(1<<14))) {
DBG("v4: pkt src/dst %pI4/%pI4 has IP options or is fragmented, dropping\n",
&iph->daddr, &iph->saddr);
goto out;
}