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netfilter: nft_payload: access GRE payload via inner offset

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Parse GRE v0 packets to properly set up inner offset, this allow for
matching on inner headers.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Pablo Neira Ayuso 2022-10-17 13:03:29 +02:00
parent d037abc241
commit c247897d7c
1 changed files with 32 additions and 0 deletions
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32
net/netfilter/nft_payload.c
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@ -19,6 +19,7 @@
/* For layer 4 checksum field offset. */
#include <linux/tcp.h>
#include <linux/udp.h>
#include <net/gre.h>
#include <linux/icmpv6.h>
#include <linux/ip.h>
#include <linux/ipv6.h>
@ -100,6 +101,37 @@ static int __nft_payload_inner_offset(struct nft_pktinfo *pkt)
pkt->inneroff = thoff + __tcp_hdrlen(th);
}
break;
case IPPROTO_GRE: {
u32 offset = sizeof(struct gre_base_hdr), version;
struct gre_base_hdr *gre, _gre;
gre = skb_header_pointer(pkt->skb, thoff, sizeof(_gre), &_gre);
if (!gre)
return -1;
version = gre->flags & GRE_VERSION;
switch (version) {
case GRE_VERSION_0:
if (gre->flags & GRE_ROUTING)
return -1;
if (gre->flags & GRE_CSUM) {
offset += sizeof_field(struct gre_full_hdr, csum) +
sizeof_field(struct gre_full_hdr, reserved1);
}
if (gre->flags & GRE_KEY)
offset += sizeof_field(struct gre_full_hdr, key);
if (gre->flags & GRE_SEQ)
offset += sizeof_field(struct gre_full_hdr, seq);
break;
default:
return -1;
}
pkt->inneroff = thoff + offset;
}
break;
default:
return -1;
}