[INET]: Make inet_create try to load protocol modules

Syntax is net-pf-PROTOCOL_FAMILY-PROTOCOL-SOCK_TYPE and if this
fails net-pf-PROTOCOL_FAMILY-PROTOCOL.

Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 25 insertions, 4 deletions

diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 52f5ecc58c46..20f52b5f5dea 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -228,12 +228,14 @@ static int inet_create(struct socket *sock, int protocol)
         struct proto *answer_prot;
         unsigned char answer_flags;
         char answer_no_check;
-        int err;
+        int try_loading_module = 0;
+        int err = -ESOCKTNOSUPPORT;
 
         sock->state = SS_UNCONNECTED;
 
         /* Look for the requested type/protocol pair. */
         answer = NULL;
+lookup_protocol:
         rcu_read_lock();
         list_for_each_rcu(p, &inetsw[sock->type]) {
                 answer = list_entry(p, struct inet_protosw, list);
@@ -254,9 +256,28 @@ static int inet_create(struct socket *sock, int protocol)
                 answer = NULL;
         }
 
-        err = -ESOCKTNOSUPPORT;
-        if (!answer)
-                goto out_rcu_unlock;
+        if (unlikely(answer == NULL)) {
+                if (try_loading_module < 2) {
+                        rcu_read_unlock();
+                        /*
+                         * Be more specific, e.g. net-pf-2-proto-132-type-1
+                         * (net-pf-PF_INET-proto-IPPROTO_SCTP-type-SOCK_STREAM)
+                         */
+                        if (++try_loading_module == 1)
+                                request_module("net-pf-%d-proto-%d-type-%d",
+                                               PF_INET, protocol, sock->type);
+                        /*
+                         * Fall back to generic, e.g. net-pf-2-proto-132
+                         * (net-pf-PF_INET-proto-IPPROTO_SCTP)
+                         */
+                        else
+                                request_module("net-pf-%d-proto-%d",
+                                               PF_INET, protocol);
+                        goto lookup_protocol;
+                } else
+                        goto out_rcu_unlock;
+        }
+
         err = -EPERM;
         if (answer->capability > 0 && !capable(answer->capability))
                 goto out_rcu_unlock;