[PATCH 3.16 099/134] ip6_tunnel: Fix missing tunnel encapsulation limit option

Ben Hutchings
2017-08-18T13:15:51Z

From: Craig Gallek <cgallek@google.com>

commit 89a23c8b528bd2c89f3981573d6cd7d23840c8a6 upstream.

The IPv6 tunneling code tries to insert IPV6_TLV_TNL_ENCAP_LIMIT and
IPV6_TLV_PADN options when an encapsulation limit is defined (the
default is a limit of 4). An MTU adjustment is done to account for
these options as well. However, the options are never present in the
generated packets.

The issue appears to be a subtlety between IPV6_DSTOPTS and
IPV6_RTHDRDSTOPTS defined in RFC 3542. When the IPIP tunnel driver was
written, the encap limit options were included as IPV6_RTHDRDSTOPTS in
dst0opt of struct ipv6_txoptions. Later, ipv6_push_nfrags_opts was
(correctly) updated to require IPV6_RTHDR options when IPV6_RTHDRDSTOPTS
are to be used. This caused the options to no longer be included in v6
encapsulated packets.

The fix is to use IPV6_DSTOPTS (in dst1opt of struct ipv6_txoptions)
instead. IPV6_DSTOPTS do not have the additional IPV6_RTHDR requirement.

Fixes: 1df64a8569c7: ("[IPV6]: Add ip6ip6 tunnel driver.")
Fixes: 333fad5364d6: ("[IPV6]: Support several new sockopt / ancillary data in Advanced API (RFC3542)")
Signed-off-by: Craig Gallek <kraig@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
net/ipv6/ip6_tunnel.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

--- a/net/ipv6/ip6_tunnel.c
+++ b/net/ipv6/ip6_tunnel.c
@@ -883,7 +883,7 @@ static void init_tel_txopt(struct ipv6_t
opt->dst_opt[5] = IPV6_TLV_PADN;
opt->dst_opt[6] = 1;

- opt->ops.dst0opt = (struct ipv6_opt_hdr *) opt->dst_opt;
+ opt->ops.dst1opt = (struct ipv6_opt_hdr *) opt->dst_opt;
opt->ops.opt_nflen = 8;
}

@@ -1051,7 +1051,7 @@ static int ip6_tnl_xmit2(struct sk_buff
proto = fl6->flowi6_proto;
if (encap_limit >= 0) {
init_tel_txopt(&opt, encap_limit);
- ipv6_push_nfrag_opts(skb, &opt.ops, &proto, NULL);
+ ipv6_push_frag_opts(skb, &opt.ops, &proto);
}

if (likely(!skb->encapsulation)) {