[PATCH 3.18 08/33] sctp: fix src address selection if using secondary addresses for ipv6

Greg Kroah-Hartman
2017-06-05T17:35:29Z

From: Xin Long <lucien.xin@gmail.com>

[ Upstream commit dbc2b5e9a09e9a6664679a667ff81cff6e5f2641 ]

Commit 0ca50d12fe46 ("sctp: fix src address selection if using secondary
addresses") has fixed a src address selection issue when using secondary
addresses for ipv4.

Now sctp ipv6 also has the similar issue. When using a secondary address,
sctp_v6_get_dst tries to choose the saddr which has the most same bits
with the daddr by sctp_v6_addr_match_len. It may make some cases not work
as expected.

hostA:
[1] fd21:356b:459a:cf10::11 (eth1)
[2] fd21:356b:459a:cf20::11 (eth2)

hostB:
[a] fd21:356b:459a:cf30::2 (eth1)
[b] fd21:356b:459a:cf40::2 (eth2)

route from hostA to hostB:
fd21:356b:459a:cf30::/64 dev eth1 metric 1024 mtu 1500

The expected path should be:
fd21:356b:459a:cf10::11 <-> fd21:356b:459a:cf30::2
But addr[2] matches addr[a] more bits than addr[1] does, according to
sctp_v6_addr_match_len. It causes the path to be:
fd21:356b:459a:cf20::11 <-> fd21:356b:459a:cf30::2

This patch is to fix it with the same way as Marcelo's fix for sctp ipv4.
As no ip_dev_find for ipv6, this patch is to use ipv6_chk_addr to check
if the saddr is in a dev instead.

Note that for backwards compatibility, it will still do the addr_match_len
check here when no optimal is found.

Reported-by: Patrick Talbert <ptalbert@redhat.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/sctp/ipv6.c | 46 +++++++++++++++++++++++++++++-----------------
1 file changed, 29 insertions(+), 17 deletions(-)

--- a/net/sctp/ipv6.c
+++ b/net/sctp/ipv6.c
@@ -239,12 +239,10 @@ static void sctp_v6_get_dst(struct sctp_
struct sctp_bind_addr *bp;
struct ipv6_pinfo *np = inet6_sk(sk);
struct sctp_sockaddr_entry *laddr;
- union sctp_addr *baddr = NULL;
union sctp_addr *daddr = &t->ipaddr;
union sctp_addr dst_saddr;
struct in6_addr *final_p, final;
__u8 matchlen = 0;
- __u8 bmatchlen;
sctp_scope_t scope;

memset(fl6, 0, sizeof(struct flowi6));
@@ -311,23 +309,37 @@ static void sctp_v6_get_dst(struct sctp_
*/
rcu_read_lock();
list_for_each_entry_rcu(laddr, &bp->address_list, list) {
- if (!laddr->valid)
+ struct dst_entry *bdst;
+ __u8 bmatchlen;
+
+ if (!laddr->valid ||
+ laddr->state != SCTP_ADDR_SRC ||
+ laddr->a.sa.sa_family != AF_INET6 ||
+ scope > sctp_scope(&laddr->a))
continue;
- if ((laddr->state == SCTP_ADDR_SRC) &&
- (laddr->a.sa.sa_family == AF_INET6) &&
- (scope <= sctp_scope(&laddr->a))) {
- bmatchlen = sctp_v6_addr_match_len(daddr, &laddr->a);
- if (!baddr || (matchlen < bmatchlen)) {
- baddr = &laddr->a;
- matchlen = bmatchlen;
- }
- }
- }
- if (baddr) {
- fl6->saddr = baddr->v6.sin6_addr;
- fl6->fl6_sport = baddr->v6.sin6_port;
+
+ fl6->saddr = laddr->a.v6.sin6_addr;
+ fl6->fl6_sport = laddr->a.v6.sin6_port;
final_p = fl6_update_dst(fl6, rcu_dereference(np->opt), &final);
- dst = ip6_dst_lookup_flow(sk, fl6, final_p);
+ bdst = ip6_dst_lookup_flow(sk, fl6, final_p);
+
+ if (!IS_ERR(bdst) &&
+ ipv6_chk_addr(dev_net(bdst->dev),
+ &laddr->a.v6.sin6_addr, bdst->dev, 1)) {
+ if (!IS_ERR_OR_NULL(dst))
+ dst_release(dst);
+ dst = bdst;
+ break;
+ }
+
+ bmatchlen = sctp_v6_addr_match_len(daddr, &laddr->a);
+ if (matchlen > bmatchlen)
+ continue;
+
+ if (!IS_ERR_OR_NULL(dst))
+ dst_release(dst);
+ dst = bdst;
+ matchlen = bmatchlen;
}
rcu_read_unlock();