CVS commit: src/sys/net/npf

["Maxime Villard" <maxv%netbsd.org@localhost>]

Module Name:    src
Committed By:   maxv
Date:           Tue Mar 13 09:04:03 UTC 2018

Modified Files:
        src/sys/net/npf: npf_handler.c npf_inet.c

Log Message:
Fix two consecutive mistakes.

The first mistake was npf_inet.c rev1.37:

        "Don't reassemble ipv6 fragments, instead treat the first fragment
        as a regular packet (subject to filtering rules), and pass
        subsequent fragments in the same group unconditionally."

Doing this was entirely wrong, because then a packet just had to push
the L4 payload in a secondary fragment, and NPF wouldn't apply rules on
it - meaning any IPv6 packet could bypass >=L4 filtering. This mistake
was supposed to be a fix for the second mistake.

The second mistake was that ip6_reass_packet (in npf_reassembly) was
getting called with npc->npc_hlen. But npc_hlen pointed to the last
encountered header in the IPv6 chain, which was not necessarily the
fragment header. So ip6_reass_packet was given garbage, and would fail,
resulting in the packet getting kicked. So basically IPv6 was broken by
NPF.

The first mistake is reverted, and the second one is fixed by doing:

-                       hlen = sizeof(struct ip6_frag);
+                       hlen = 0;

Now the iteration stops on the fragment header, and the call to
ip6_reass_packet is valid.

My npf_inet.c rev1.38 is partially reverted: we don't need to worry
about failing properly to advance; once the packet is reassembled
npf_cache_ip gets called again, and this time the whole chain should be
there.

Tested with a simple UDPv6 server - send a 3000-byte-sized buffer, the
packet gets correctly reassembled by NPF now.


To generate a diff of this commit:
cvs rdiff -u -r1.38 -r1.39 src/sys/net/npf/npf_handler.c
cvs rdiff -u -r1.39 -r1.40 src/sys/net/npf/npf_inet.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.