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>

3 files changed, 20 insertions, 29 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
  *
diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index b99ca4e154b9..0f3185a662c3 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -113,19 +113,6 @@ int ip_local_out(struct sk_buff *skb)
 }
 EXPORT_SYMBOL_GPL(ip_local_out);
 
-/* dev_loopback_xmit for use with netfilter. */
-static int ip_dev_loopback_xmit(struct sk_buff *newskb)
-{
-        skb_reset_mac_header(newskb);
-        __skb_pull(newskb, skb_network_offset(newskb));
-        newskb->pkt_type = PACKET_LOOPBACK;
-        newskb->ip_summed = CHECKSUM_UNNECESSARY;
-        WARN_ON(!skb_dst(newskb));
-        skb_dst_force(newskb);
-        netif_rx_ni(newskb);
-        return 0;
-}
-
 static inline int ip_select_ttl(struct inet_sock *inet, struct dst_entry *dst)
 {
         int ttl = inet->uc_ttl;
@@ -281,7 +268,7 @@ int ip_mc_output(struct sk_buff *skb)
                         if (newskb)
                                 NF_HOOK(NFPROTO_IPV4, NF_INET_POST_ROUTING,
                                         newskb, NULL, newskb->dev,
-                                        ip_dev_loopback_xmit);
+                                        dev_loopback_xmit);
                 }
 
                 /* Multicasts with ttl 0 must not go beyond the host */
@@ -296,7 +283,7 @@ int ip_mc_output(struct sk_buff *skb)
                 struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
                 if (newskb)
                         NF_HOOK(NFPROTO_IPV4, NF_INET_POST_ROUTING, newskb,
-                                NULL, newskb->dev, ip_dev_loopback_xmit);
+                                NULL, newskb->dev, dev_loopback_xmit);
         }
 
         return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING, skb, NULL,
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 62fcf3e48aca..ee1bb450bfe4 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -83,19 +83,6 @@ int ip6_local_out(struct sk_buff *skb)
 }
 EXPORT_SYMBOL_GPL(ip6_local_out);
 
-/* dev_loopback_xmit for use with netfilter. */
-static int ip6_dev_loopback_xmit(struct sk_buff *newskb)
-{
-        skb_reset_mac_header(newskb);
-        __skb_pull(newskb, skb_network_offset(newskb));
-        newskb->pkt_type = PACKET_LOOPBACK;
-        newskb->ip_summed = CHECKSUM_UNNECESSARY;
-        WARN_ON(!skb_dst(newskb));
-
-        netif_rx_ni(newskb);
-        return 0;
-}
-
 static int ip6_finish_output2(struct sk_buff *skb)
 {
         struct dst_entry *dst = skb_dst(skb);
@@ -121,7 +108,7 @@ static int ip6_finish_output2(struct sk_buff *skb)
                         if (newskb)
                                 NF_HOOK(NFPROTO_IPV6, NF_INET_POST_ROUTING,
                                         newskb, NULL, newskb->dev,
-                                        ip6_dev_loopback_xmit);
+                                        dev_loopback_xmit);
 
                         if (ipv6_hdr(skb)->hop_limit == 0) {
                                 IP6_INC_STATS(dev_net(dev), idev,