net-next: add dev_loopback_xmit() to avoid duplicate code

Add dev_loopback_xmit() in order to deduplicate functions
ip_dev_loopback_xmit() (in net/ipv4/ip_output.c) and
ip6_dev_loopback_xmit() (in net/ipv6/ip6_output.c).

I was about to reinvent the wheel when I noticed that
ip_dev_loopback_xmit() and ip6_dev_loopback_xmit() do exactly what I
need and are not IP-only functions, but they were not available to reuse
elsewhere.

ip6_dev_loopback_xmit() does not have line "skb_dst_force(skb);", but I
understand that this is harmless, and should be in dev_loopback_xmit().

Signed-off-by: Michel Machado <michel@digirati.com.br>
CC: "David S. Miller" <davem@davemloft.net>
CC: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
CC: James Morris <jmorris@namei.org>
CC: Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>
CC: Patrick McHardy <kaber@trash.net>
CC: Eric Dumazet <edumazet@google.com>
CC: Jiri Pirko <jpirko@redhat.com>
CC: "Michał Mirosław" <mirq-linux@rere.qmqm.pl>
CC: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 17 insertions, 0 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index cd0981977f5c..c6e29ea65bd9 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2476,6 +2476,23 @@ static DEFINE_PER_CPU(int, xmit_recursion);
 #define RECURSION_LIMIT 10
 
 /**
+ *      dev_loopback_xmit - loop back @skb
+ *      @skb: buffer to transmit
+ */
+int dev_loopback_xmit(struct sk_buff *skb)
+{
+        skb_reset_mac_header(skb);
+        __skb_pull(skb, skb_network_offset(skb));
+        skb->pkt_type = PACKET_LOOPBACK;
+        skb->ip_summed = CHECKSUM_UNNECESSARY;
+        WARN_ON(!skb_dst(skb));
+        skb_dst_force(skb);
+        netif_rx_ni(skb);
+        return 0;
+}
+EXPORT_SYMBOL(dev_loopback_xmit);
+
+/**
  *      dev_queue_xmit - transmit a buffer
  *      @skb: buffer to transmit
  *