Subject: Re: ipv6 udp early demux breaks udp_l3mdev_accept=0

From: Subash Abhinov Kasiviswanathan <[email-masked]>
Date: Sat, 15 Apr 2017 20:23:31 -0600

>> It should be fixed for 4.12. Basically, __udp6_lib_demux_lookup needs 
>> to
>> be more like __udp4_lib_demux_lookup

Hi David

Would it be possible for you to test this with udp_l3mdev_accept=0

diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index b793ed1..0e307e5 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)