Merge branch 'replace-dst_confirm'

Julian Anastasov says:

====================
net: dst_confirm replacement

	This patchset addresses the problem of neighbour
confirmation where received replies from one nexthop
can cause confirmation of different nexthop when using
the same dst. Thanks to YueHaibing <yuehaibing@huawei.com>
for tracking the dst->pending_confirm problem.

	Sockets can obtain cached output route. Such
routes can be to known nexthop (rt_gateway=IP) or to be
used simultaneously for different nexthop IPs by different
subnet prefixes (nh->nh_scope = RT_SCOPE_HOST, rt_gateway=0).

	At first look, there are more problems:

- dst_confirm() sets flag on dst and not on dst->path,
as result, indication is lost when XFRM is used

- DNAT can change the nexthop, so the really used nexthop is
not confirmed

	So, the following solution is to avoid using
dst->pending_confirm.

	The current dst_confirm() usage is as follows:

Protocols confirming dst on received packets:
- TCP (1 dst per socket)
- SCTP (1 dst per transport)
- CXGB*

Protocols supporting sendmsg with MSG_CONFIRM [ | MSG_PROBE ] to
confirm neighbour:
- UDP IPv4/IPv6
- ICMPv4 PING
- RAW IPv4/IPv6
- L2TP/IPv6

MSG_CONFIRM for other purposes (fix not needed):
- CAN

Sending without locking the socket:
- UDP (when no cork)
- RAW (when hdrincl=1)

Redirects from old to new GW:
- rt6_do_redirect

	The patchset includes the following changes:

1. sock: add sk_dst_pending_confirm flag

- used only by TCP with patch 4 to remember the received
indication in sk->sk_dst_pending_confirm

2. net: add dst_pending_confirm flag to skbuff

- skb->dst_pending_confirm will be used by all protocols
in following patches, via skb_{set,get}_dst_pending_confirm

3. sctp: add dst_pending_confirm flag

- SCTP uses per-transport dsts and can not use
sk->sk_dst_pending_confirm like TCP

4. tcp: replace dst_confirm with sk_dst_confirm

5. net: add confirm_neigh method to dst_ops

- IPv4 and IPv6 provision for slow neigh lookups for MSG_PROBE users.
I decided to use neigh lookup only for this case because on
MSG_PROBE the skb may pass MTU checks but it does not reach
the neigh confirmation code. This patch will be used from patch 6.

- xfrm_confirm_neigh: we use the last tunnel address, if present.
When there are only transports, the original dest address is used.

6. net: use dst_confirm_neigh for UDP, RAW, ICMP, L2TP

- dst_confirm conversion for UDP, RAW, ICMP and L2TP/IPv6

- these protocols use MSG_CONFIRM propagated by ip*_append_data
to skb->dst_pending_confirm. sk->sk_dst_pending_confirm is not
used because some sending paths do not lock the socket. For
MSG_PROBE we use the slow lookup (dst_confirm_neigh).

- there are also 2 cases that need the slow lookup:
__ip6_rt_update_pmtu and rt6_do_redirect. I hope
&ipv6_hdr(skb)->saddr is the correct nexthop address to use here.

7. net: pending_confirm is not used anymore

- I failed to understand the CXGB* code, I see dst_confirm()
calls but I'm not sure dst_neigh_output() was called. For now
I just removed the dst->pending_confirm flag and left all
dst_confirm() calls there. Any better idea?

- Now may be old function neigh_output() should be restored
instead of dst_neigh_output?
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 9 insertions, 12 deletions

diff --git a/include/net/dst.h b/include/net/dst.h
index 6835d224d47b..84a1043dd6a1 100644
--- a/include/net/dst.h
+++ b/include/net/dst.h
@@ -59,8 +59,6 @@ struct dst_entry {
 #define DST_XFRM_QUEUE		0x0100
 #define DST_METADATA		0x0200
 
-	unsigned short		pending_confirm;
-
 	short			error;
 
 	/* A non-zero value of dst->obsolete forces by-hand validation
@@ -78,6 +76,8 @@ struct dst_entry {
 #define DST_OBSOLETE_KILL	-2
 	unsigned short		header_len;	/* more space at head required */
 	unsigned short		trailer_len;	/* space to reserve at tail */
+	unsigned short		__pad3;
+
 #ifdef CONFIG_IP_ROUTE_CLASSID
 	__u32			tclassid;
 #else
@@ -440,7 +440,6 @@ static inline void dst_rcu_free(struct rcu_head *head)
 
 static inline void dst_confirm(struct dst_entry *dst)
 {
-	dst->pending_confirm = 1;
 }
 
 static inline int dst_neigh_output(struct dst_entry *dst, struct neighbour *n,
@@ -448,15 +447,6 @@ static inline int dst_neigh_output(struct dst_entry *dst, struct neighbour *n,
 {
 	const struct hh_cache *hh;
 
-	if (dst->pending_confirm) {
-		unsigned long now = jiffies;
-
-		dst->pending_confirm = 0;
-		/* avoid dirtying neighbour */
-		if (n->confirmed != now)
-			n->confirmed = now;
-	}
-
 	hh = &n->hh;
 	if ((n->nud_state & NUD_CONNECTED) && hh->hh_len)
 		return neigh_hh_output(hh, skb);
@@ -477,6 +467,13 @@ static inline struct neighbour *dst_neigh_lookup_skb(const struct dst_entry *dst
 	return IS_ERR(n) ? NULL : n;
 }
 
+static inline void dst_confirm_neigh(const struct dst_entry *dst,
+				     const void *daddr)
+{
+	if (dst->ops->confirm_neigh)
+		dst->ops->confirm_neigh(dst, daddr);
+}
+
 static inline void dst_link_failure(struct sk_buff *skb)
 {
 	struct dst_entry *dst = skb_dst(skb);