ipv6: Kill ipv6 dependency of icmpv6_send().

Following patch adds icmp-registration module for ipv6.  It allows
ipv6 protocol to register icmp_sender which is used for sending
ipv6 icmp msgs.  This extra layer allows us to kill ipv6 dependency
for sending icmp packets.

This patch also fixes ip_tunnel compilation problem when ip_tunnel
is statically compiled in kernel but ipv6 is module

Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 68 insertions, 16 deletions

diff --git a/net/ipv6/Makefile b/net/ipv6/Makefile
index 309af19a0a0a..9af088d2cdaa 100644
--- a/net/ipv6/Makefile
+++ b/net/ipv6/Makefile
@@ -40,7 +40,7 @@ obj-$(CONFIG_IPV6_SIT) += sit.o
 obj-$(CONFIG_IPV6_TUNNEL) += ip6_tunnel.o
 obj-$(CONFIG_IPV6_GRE) += ip6_gre.o
 
-obj-y += addrconf_core.o exthdrs_core.o ip6_checksum.o
+obj-y += addrconf_core.o exthdrs_core.o ip6_checksum.o ip6_icmp.o
 obj-$(CONFIG_INET) += output_core.o protocol.o $(ipv6-offload)
 
 obj-$(subst m,y,$(CONFIG_IPV6)) += inet6_hashtables.o
diff --git a/net/ipv6/icmp.c b/net/ipv6/icmp.c
index 71b900c3f4ff..2a53a790514d 100644
--- a/net/ipv6/icmp.c
+++ b/net/ipv6/icmp.c
@@ -124,15 +124,6 @@ static __inline__ void icmpv6_xmit_unlock(struct sock *sk)
 }
 
 /*
- * Slightly more convenient version of icmpv6_send.
- */
-void icmpv6_param_prob(struct sk_buff *skb, u8 code, int pos)
-{
-        icmpv6_send(skb, ICMPV6_PARAMPROB, code, pos);
-        kfree_skb(skb);
-}
-
-/*
  * Figure out, may we reply to this packet with icmp error.
  *
  * We do not reply, if:
@@ -332,7 +323,7 @@ static struct dst_entry *icmpv6_route_lookup(struct net *net, struct sk_buff *sk
          * anycast.
          */
         if (((struct rt6_info *)dst)->rt6i_flags & RTF_ANYCAST) {
-                LIMIT_NETDEBUG(KERN_DEBUG "icmpv6_send: acast source\n");
+                LIMIT_NETDEBUG(KERN_DEBUG "icmp6_send: acast source\n");
                 dst_release(dst);
                 return ERR_PTR(-EINVAL);
         }
@@ -381,7 +372,7 @@ relookup_failed:
 /*
  *      Send an ICMP message in response to a packet in error
  */
-void icmpv6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info)
+static void icmp6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info)
 {
         struct net *net = dev_net(skb->dev);
         struct inet6_dev *idev = NULL;
@@ -406,7 +397,7 @@ void icmpv6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info)
         /*
          *      Make sure we respect the rules
          *      i.e. RFC 1885 2.4(e)
-         *      Rule (e.1) is enforced by not using icmpv6_send
+         *      Rule (e.1) is enforced by not using icmp6_send
          *      in any code that processes icmp errors.
          */
         addr_type = ipv6_addr_type(&hdr->daddr);
@@ -444,7 +435,7 @@ void icmpv6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info)
          *      and anycast addresses will be checked later.
          */
         if ((addr_type == IPV6_ADDR_ANY) || (addr_type & IPV6_ADDR_MULTICAST)) {
-                LIMIT_NETDEBUG(KERN_DEBUG "icmpv6_send: addr_any/mcast source\n");
+                LIMIT_NETDEBUG(KERN_DEBUG "icmp6_send: addr_any/mcast source\n");
                 return;
         }
 
@@ -452,7 +443,7 @@ void icmpv6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info)
          *      Never answer to a ICMP packet.
          */
         if (is_ineligible(skb)) {
-                LIMIT_NETDEBUG(KERN_DEBUG "icmpv6_send: no reply to icmp error\n");
+                LIMIT_NETDEBUG(KERN_DEBUG "icmp6_send: no reply to icmp error\n");
                 return;
         }
 
@@ -529,7 +520,14 @@ out_dst_release:
 out:
         icmpv6_xmit_unlock(sk);
 }
-EXPORT_SYMBOL(icmpv6_send);
+
+/* Slightly more convenient version of icmp6_send.
+ */
+void icmpv6_param_prob(struct sk_buff *skb, u8 code, int pos)
+{
+        icmp6_send(skb, ICMPV6_PARAMPROB, code, pos);
+        kfree_skb(skb);
+}
 
 static void icmpv6_echo_reply(struct sk_buff *skb)
 {
@@ -885,8 +883,14 @@ int __init icmpv6_init(void)
         err = -EAGAIN;
         if (inet6_add_protocol(&icmpv6_protocol, IPPROTO_ICMPV6) < 0)
                 goto fail;
+
+        err = inet6_register_icmp_sender(icmp6_send);
+        if (err)
+                goto sender_reg_err;
         return 0;
 
+sender_reg_err:
+        inet6_del_protocol(&icmpv6_protocol, IPPROTO_ICMPV6);
 fail:
         pr_err("Failed to register ICMP6 protocol\n");
         unregister_pernet_subsys(&icmpv6_sk_ops);
@@ -895,6 +899,7 @@ fail:
 
 void icmpv6_cleanup(void)
 {
+        inet6_unregister_icmp_sender(icmp6_send);
         unregister_pernet_subsys(&icmpv6_sk_ops);
         inet6_del_protocol(&icmpv6_protocol, IPPROTO_ICMPV6);
 }
diff --git a/net/ipv6/ip6_icmp.c b/net/ipv6/ip6_icmp.c
new file mode 100644
index 000000000000..4578e23834f7
--- /dev/null
+++ b/net/ipv6/ip6_icmp.c
@@ -0,0 +1,47 @@
+#include <linux/export.h>
+#include <linux/icmpv6.h>
+#include <linux/mutex.h>
+#include <linux/netdevice.h>
+#include <linux/spinlock.h>
+
+#include <net/ipv6.h>
+
+#if IS_ENABLED(CONFIG_IPV6)
+
+static ip6_icmp_send_t __rcu *ip6_icmp_send;
+
+int inet6_register_icmp_sender(ip6_icmp_send_t *fn)
+{
+        return (cmpxchg((ip6_icmp_send_t **)&ip6_icmp_send, NULL, fn) == NULL) ?
+                0 : -EBUSY;
+}
+EXPORT_SYMBOL(inet6_register_icmp_sender);
+
+int inet6_unregister_icmp_sender(ip6_icmp_send_t *fn)
+{
+        int ret;
+
+        ret = (cmpxchg((ip6_icmp_send_t **)&ip6_icmp_send, fn, NULL) == fn) ?
+              0 : -EINVAL;
+
+        synchronize_net();
+
+        return ret;
+}
+EXPORT_SYMBOL(inet6_unregister_icmp_sender);
+
+void icmpv6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info)
+{
+        ip6_icmp_send_t *send;
+
+        rcu_read_lock();
+        send = rcu_dereference(ip6_icmp_send);
+
+        if (!send)
+                goto out;
+        send(skb, type, code, info);
+out:
+        rcu_read_unlock();
+}
+EXPORT_SYMBOL(icmpv6_send);
+#endif