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

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Message-ID: <lsq.1503062000.960820119@decadent.org.uk>
Date:   Fri, 18 Aug 2017 14:13:20 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Craig Gallek" <kraig@...gle.com>,
        "Craig Gallek" <cgallek@...gle.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 3.16 099/134] ip6_tunnel: Fix missing tunnel encapsulation
 limit option

3.16.47-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Craig Gallek <cgallek@...gle.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@...gle.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.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)) {