[PATCH net-next 3/5] udp: do not touch socket refcount in early demux

[Paolo Abeni]

use noref sockets instead. This gives some small performance
improvements and will allow efficient early demux for unconnected
sockets in a later patch.

Signed-off-by: Paolo Abeni <pab...@redhat.com>
---
 net/ipv4/udp.c | 18 ++++++++++--------
 net/ipv6/udp.c | 10 ++++++----
 2 files changed, 16 insertions(+), 12 deletions(-)

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 784ced0b9150..ba49d5aa9f09 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -2050,12 +2050,13 @@ static inline int udp4_csum_init(struct sk_buff *skb, 
struct udphdr *uh,
 int __udp4_lib_rcv(struct sk_buff *skb, struct udp_table *udptable,
                   int proto)
 {
-       struct sock *sk;
-       struct udphdr *uh;
-       unsigned short ulen;
+       struct net *net = dev_net(skb->dev);
        struct rtable *rt = skb_rtable(skb);
+       unsigned short ulen;
        __be32 saddr, daddr;
-       struct net *net = dev_net(skb->dev);
+       struct udphdr *uh;
+       struct sock *sk;
+       bool noref_sk;
 
        /*
         *  Validate the packet.
@@ -2081,6 +2082,7 @@ int __udp4_lib_rcv(struct sk_buff *skb, struct udp_table 
*udptable,
        if (udp4_csum_init(skb, uh, proto))
                goto csum_error;
 
+       noref_sk = skb_has_noref_sk(skb);
        sk = skb_steal_sock(skb);
        if (sk) {
                struct dst_entry *dst = skb_dst(skb);
@@ -2090,7 +2092,8 @@ int __udp4_lib_rcv(struct sk_buff *skb, struct udp_table 
*udptable,
                        udp_sk_rx_dst_set(sk, dst);
 
                ret = udp_queue_rcv_skb(sk, skb);
-               sock_put(sk);
+               if (!noref_sk)
+                       sock_put(sk);
                /* a return value > 0 means to resubmit the input, but
                 * it wants the return to be -protocol, or 0
                 */
@@ -2261,11 +2264,10 @@ void udp_v4_early_demux(struct sk_buff *skb)
                                             uh->source, iph->saddr, dif, sdif);
        }
 
-       if (!sk || !refcount_inc_not_zero(&sk->sk_refcnt))
+       if (!sk)
                return;
 
-       skb->sk = sk;
-       skb->destructor = sock_efree;
+       skb_set_noref_sk(skb, sk);
        dst = READ_ONCE(sk->sk_rx_dst);
 
        if (dst)
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index e2ecfb137297..8f62392c4c35 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -787,6 +787,7 @@ int __udp6_lib_rcv(struct sk_buff *skb, struct udp_table 
*udptable,
        struct net *net = dev_net(skb->dev);
        struct udphdr *uh;
        struct sock *sk;
+       bool noref_sk;
        u32 ulen = 0;
 
        if (!pskb_may_pull(skb, sizeof(struct udphdr)))
@@ -823,6 +824,7 @@ int __udp6_lib_rcv(struct sk_buff *skb, struct udp_table 
*udptable,
                goto csum_error;
 
        /* Check if the socket is already available, e.g. due to early demux */
+       noref_sk = skb_has_noref_sk(skb);
        sk = skb_steal_sock(skb);
        if (sk) {
                struct dst_entry *dst = skb_dst(skb);
@@ -832,7 +834,8 @@ int __udp6_lib_rcv(struct sk_buff *skb, struct udp_table 
*udptable,
                        udp6_sk_rx_dst_set(sk, dst);
 
                ret = udpv6_queue_rcv_skb(sk, skb);
-               sock_put(sk);
+               if (!noref_sk)
+                       sock_put(sk);
 
                /* a return value > 0 means to resubmit the input */
                if (ret > 0)
@@ -948,11 +951,10 @@ static void udp_v6_early_demux(struct sk_buff *skb)
        else
                return;
 
-       if (!sk || !refcount_inc_not_zero(&sk->sk_refcnt))
+       if (!sk)
                return;
 
-       skb->sk = sk;
-       skb->destructor = sock_efree;
+       skb_set_noref_sk(skb, sk);
        dst = READ_ONCE(sk->sk_rx_dst);
 
        if (dst)
-- 
2.13.5