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netfilter: nf_conntrack_reasm: properly handle packets fragmented into a single fragment

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When an ICMPV6_PKT_TOOBIG message is received with a MTU below 1280,
all further packets include a fragment header.

Unlike regular defragmentation, conntrack also needs to "reassemble"
those fragments in order to obtain a packet without the fragment
header for connection tracking. Currently nf_conntrack_reasm checks
whether a fragment has either IP6_MF set or an offset != 0, which
makes it ignore those fragments.

Remove the invalid check and make reassembly handle fragment queues
containing only a single fragment.

Reported-and-tested-by: Ulrich Weber <uweber@astaro.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>
This commit is contained in:
Patrick McHardy 2010-02-19 18:18:37 +01:00
parent 64507fdbc2
commit 9e2dcf7202
1 changed files with 1 additions and 7 deletions
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8
net/ipv6/netfilter/nf_conntrack_reasm.c
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@ -469,7 +469,7 @@ nf_ct_frag6_reasm(struct nf_ct_frag6_queue *fq, struct net_device *dev)
/* all original skbs are linked into the NFCT_FRAG6_CB(head).orig */
fp = skb_shinfo(head)->frag_list;
if (NFCT_FRAG6_CB(fp)->orig == NULL)
if (fp && NFCT_FRAG6_CB(fp)->orig == NULL)
/* at above code, head skb is divided into two skbs. */
fp = fp->next;
@ -595,12 +595,6 @@ struct sk_buff *nf_ct_frag6_gather(struct sk_buff *skb, u32 user)
hdr = ipv6_hdr(clone);
fhdr = (struct frag_hdr *)skb_transport_header(clone);
if (!(fhdr->frag_off & htons(0xFFF9))) {
pr_debug("Invalid fragment offset\n");
/* It is not a fragmented frame */
goto ret_orig;
}
if (atomic_read(&nf_init_frags.mem) > nf_init_frags.high_thresh)
nf_ct_frag6_evictor();