[PATCH net-next v2] net: ipv6: Fix UDP early demux lookup with udp_l3mdev_accept=0

[PATCH net-next v2] net: ipv6: Fix UDP early demux lookup with udp_l3mdev_accept=0

[Subash Abhinov Kasiviswanathan]

David Ahern reported that 5425077d73e0c ("net: ipv6: Add early demux
handler for UDP unicast") breaks udp_l3mdev_accept=0 since early
demux for IPv6 UDP was doing a generic socket lookup which does not
require an exact match. Fix this by making UDPv6 early demux match
connected sockets only.

v1->v2: Take reference to socket after match as suggested by Eric

Fixes: 5425077d73e0c ("net: ipv6: Add early demux handler for UDP unicast")
Reported-by: David Ahern <dsa@cumulusnetworks.com>
Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>
Cc: Eric Dumazet <edumazet@google.com>
---
 net/ipv6/udp.c | 23 ++++++++++++++---------
 1 file changed, 14 insertions(+), 9 deletions(-)

diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index b793ed1..5a4504b 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -46,6 +46,7 @@
 #include <net/tcp_states.h>
 #include <net/ip6_checksum.h>
 #include <net/xfrm.h>
+#include <net/inet_hashtables.h>
 #include <net/inet6_hashtables.h>
 #include <net/busy_poll.h>
 #include <net/sock_reuseport.h>
@@ -864,21 +865,25 @@ int __udp6_lib_rcv(struct sk_buff *skb, struct udp_table *udptable,
 	return 0;
 }
 
+
 static struct sock *__udp6_lib_demux_lookup(struct net *net,
 			__be16 loc_port, const struct in6_addr *loc_addr,
 			__be16 rmt_port, const struct in6_addr *rmt_addr,
 			int dif)
 {
+	unsigned short hnum = ntohs(loc_port);
+	unsigned int hash2 = udp6_portaddr_hash(net, loc_addr, hnum);
+	unsigned int slot2 = hash2 & udp_table.mask;
+	struct udp_hslot *hslot2 = &udp_table.hash2[slot2];
+	const __portpair ports = INET_COMBINED_PORTS(rmt_port, hnum);
 	struct sock *sk;
 
-	rcu_read_lock();
-	sk = __udp6_lib_lookup(net, rmt_addr, rmt_port, loc_addr, loc_port,
-			       dif, &udp_table, NULL);
-	if (sk && !atomic_inc_not_zero(&sk->sk_refcnt))
-		sk = NULL;
-	rcu_read_unlock();
-
-	return sk;
+	udp_portaddr_for_each_entry_rcu(sk, &hslot2->head) {
+		if (INET6_MATCH(sk, net, rmt_addr, loc_addr, ports, dif))
+			return sk;
+		break;
+	}
+	return NULL;
 }
 
 static void udp_v6_early_demux(struct sk_buff *skb)
@@ -903,7 +908,7 @@ static void udp_v6_early_demux(struct sk_buff *skb)
 	else
 		return;
 
-	if (!sk)
+	if (!sk || !atomic_inc_not_zero_hint(&sk->sk_refcnt, 2))
 		return;
 
 	skb->sk = sk;
-- 
1.9.1

RE: [PATCH net-next v2] net: ipv6: Fix UDP early demux lookup with udp_l3mdev_accept=0

[YUAN Linyu]

> -----Original Message-----
> From: netdev-owner@vger.kernel.org [mailto:netdev-owner@vger.kernel.org]
> On Behalf Of Subash Abhinov Kasiviswanathan
> Sent: Tuesday, April 18, 2017 7:25 AM
> To: dsa@cumulusnetworks.com; davem@davemloft.net;
> netdev@vger.kernel.org; rshearma@brocade.com; eric.dumazet@gmail.com
> Cc: Subash Abhinov Kasiviswanathan; Eric Dumazet
> Subject: [PATCH net-next v2] net: ipv6: Fix UDP early demux lookup with
> udp_l3mdev_accept=0
> 
> -	return sk;
> +	udp_portaddr_for_each_entry_rcu(sk, &hslot2->head) {
> +		if (INET6_MATCH(sk, net, rmt_addr, loc_addr, ports, dif))
> +			return sk;
> +		break;
I think break here should remove ?
> +	}
> +	return NULL;
>  }
> --
> 1.9.1

Re: [PATCH net-next v2] net: ipv6: Fix UDP early demux lookup with udp_l3mdev_accept=0

[Subash Abhinov Kasiviswanathan]

>> +		break;
> I think break here should remove ?

Hi Yuan

This is similar to __udp4_lib_demux_lookup where we need to check if the 
first
socket is an exact match or break since chains maybe long.

Re: [PATCH net-next v2] net: ipv6: Fix UDP early demux lookup with udp_l3mdev_accept=0

[David Ahern]

On 4/17/17 7:07 PM, Subash Abhinov Kasiviswanathan wrote:
>>> +        break;
>> I think break here should remove ?
> 
> Hi Yuan
> 
> This is similar to __udp4_lib_demux_lookup where we need to check if the
> first
> socket is an exact match or break since chains maybe long.
> 

I suggest adding the same comment as __udp4_lib_demux_lookup; it does
look odd.

Re: [PATCH net-next v2] net: ipv6: Fix UDP early demux lookup with udp_l3mdev_accept=0

[David Ahern]

On 4/17/17 5:24 PM, Subash Abhinov Kasiviswanathan wrote:
> David Ahern reported that 5425077d73e0c ("net: ipv6: Add early demux
> handler for UDP unicast") breaks udp_l3mdev_accept=0 since early
> demux for IPv6 UDP was doing a generic socket lookup which does not
> require an exact match. Fix this by making UDPv6 early demux match
> connected sockets only.
> 
> v1->v2: Take reference to socket after match as suggested by Eric
> 
> Fixes: 5425077d73e0c ("net: ipv6: Add early demux handler for UDP unicast")
> Reported-by: David Ahern <dsa@cumulusnetworks.com>
> Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>
> Cc: Eric Dumazet <edumazet@google.com>
> ---
>  net/ipv6/udp.c | 23 ++++++++++++++---------
>  1 file changed, 14 insertions(+), 9 deletions(-)

Besides adding the comment before the break, this looks fine to me.

Acked-by: David Ahern <dsa@cumulusnetworks.com>
Tested-by: David Ahern <dsa@cumulusnetworks.com>

If the only change for v3 is the comment before the break, please keep
the above with the new patch.