net: ip_queue_rcv_skb() helper

When queueing a skb to socket, we can immediately release its dst if
target socket do not use IP_CMSG_PKTINFO.

tcp_data_queue() can drop dst too.

This to benefit from a hot cache line and avoid the receiver, possibly
on another cpu, to dirty this cache line himself.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 19 insertions, 2 deletions

diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index b0aa0546a3b3..ce231780a2b1 100644
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -954,6 +954,22 @@ e_inval:
         return -EINVAL;
 }
 
+/**
+ * ip_queue_rcv_skb - Queue an skb into sock receive queue
+ * @sk: socket
+ * @skb: buffer
+ *
+ * Queues an skb into socket receive queue. If IP_CMSG_PKTINFO option
+ * is not set, we drop skb dst entry now, while dst cache line is hot.
+ */
+int ip_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
+{
+        if (!(inet_sk(sk)->cmsg_flags & IP_CMSG_PKTINFO))
+                skb_dst_drop(skb);
+        return sock_queue_rcv_skb(sk, skb);
+}
+EXPORT_SYMBOL(ip_queue_rcv_skb);
+
 int ip_setsockopt(struct sock *sk, int level,
                 int optname, char __user *optval, unsigned int optlen)
 {
diff --git a/net/ipv4/raw.c b/net/ipv4/raw.c
index cc6f097fbd5f..52ef5af78a45 100644
--- a/net/ipv4/raw.c
+++ b/net/ipv4/raw.c
@@ -290,7 +290,7 @@ static int raw_rcv_skb(struct sock * sk, struct sk_buff * skb)
 {
         /* Charge it to the socket. */
 
-        if (sock_queue_rcv_skb(sk, skb) < 0) {
+        if (ip_queue_rcv_skb(sk, skb) < 0) {
                 kfree_skb(skb);
                 return NET_RX_DROP;
         }
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index ae3ec15fb630..e82162c211bf 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4367,6 +4367,7 @@ static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
         if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq)
                 goto drop;
 
+        skb_dst_drop(skb);
         __skb_pull(skb, th->doff * 4);
 
         TCP_ECN_accept_cwr(tp, skb);
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 1f86965ba7d7..4560b291180b 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1264,7 +1264,7 @@ static int __udp_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
         if (inet_sk(sk)->inet_daddr)
                 sock_rps_save_rxhash(sk, skb->rxhash);
 
-        rc = sock_queue_rcv_skb(sk, skb);
+        rc = ip_queue_rcv_skb(sk, skb);
         if (rc < 0) {
                 int is_udplite = IS_UDPLITE(sk);