iptables-translate -A I -f
nft add rule ip filter I ip frag-off != 0 counter
iptables however checks:
frag_off = ntohs(iph->frag_off) & IP_OFFSET;
if (NF_INVF(ipinfo, IPT_INV_FRAG,
(ipinfo->flags & IPT_F_FRAG) && !frag_off))
return false;
So we need to mask off non-offset bits.
Second issue is that we negated the meaning in ipt-restore.
-f should match if (frag_off & IP_OFFSET) NE 0
! -f matches non-fragmented packets, i.e.
frag_off & IP_OFFSET == 0.
So we cannot use nft_invflags2cmp(), as that will use
NEQ for negation, but we need EQ instead here.
Signed-off-by: Florian Westphal <[email protected]>
---
iptables/nft-ipv4.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/iptables/nft-ipv4.c b/iptables/nft-ipv4.c
index ef8c06eaa369..bdf478d1be5b 100644
--- a/iptables/nft-ipv4.c
+++ b/iptables/nft-ipv4.c
@@ -65,10 +65,13 @@ static int nft_ipv4_add(struct nftnl_rule *r, void *data)
add_payload(r, offsetof(struct iphdr, frag_off), 2,
NFT_PAYLOAD_NETWORK_HEADER);
/* get the 13 bits that contain the fragment offset */
- add_bitwise_u16(r, 0x1fff, !0x1fff);
+ add_bitwise_u16(r, 0x1fff, 0);
/* if offset is non-zero, this is a fragment */
- op = nft_invflags2cmp(cs->fw.ip.invflags, IPT_INV_FRAG);
+ op = NFT_CMP_NEQ;
+ if (cs->fw.ip.invflags & IPT_INV_FRAG)
+ op = NFT_CMP_EQ;
+
add_cmp_u16(r, 0, op);
}
@@ -459,7 +462,7 @@ static int nft_ipv4_xlate(const void *data, struct xt_xlate
*xl)
cs->fw.ip.invflags & IPT_INV_VIA_OUT);
if (cs->fw.ip.flags & IPT_F_FRAG) {
- xt_xlate_add(xl, "ip frag-off %s%x ",
+ xt_xlate_add(xl, "ip frag-off & 0x1fff %s%x ",
cs->fw.ip.invflags & IPT_INV_FRAG? "" : "!= ", 0);
}
--
2.17.0
--
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