From de874054ec26a78ce83ccf13c449a4d3c4a5778e Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Sat, 5 May 2018 10:38:38 +0200 Subject: xtables-compat: fix ipv4 frag (-f) 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 --- iptables/nft-ipv4.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) (limited to 'iptables/nft-ipv4.c') diff --git a/iptables/nft-ipv4.c b/iptables/nft-ipv4.c index 8193ac3c..bddd784c 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); } @@ -453,7 +456,7 @@ 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); } -- cgit v1.2.3