[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>

3 files changed, 36 insertions, 6 deletions

diff --git a/net/dccp/proto.c b/net/dccp/proto.c
index 70284e6afe05..66c43fce17a6 100644
--- a/net/dccp/proto.c
+++ b/net/dccp/proto.c
@@ -811,8 +811,13 @@ static void __exit dccp_fini(void)
 module_init(dccp_init);
 module_exit(dccp_fini);
 
-/* __stringify doesn't likes enums, so use SOCK_DCCP (6) value directly  */
-MODULE_ALIAS("net-pf-" __stringify(PF_INET) "-6");
+/*
+ * __stringify doesn't likes enums, so use SOCK_DCCP (6) and IPPROTO_DCCP (33)
+ * values directly, Also cover the case where the protocol is not specified,
+ * i.e. net-pf-PF_INET-proto-0-type-SOCK_DCCP
+ */
+MODULE_ALIAS("net-pf-" __stringify(PF_INET) "-proto-33-type-6");
+MODULE_ALIAS("net-pf-" __stringify(PF_INET) "-proto-0-type-6");
 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Arnaldo Carvalho de Melo <acme@conectiva.com.br>");
 MODULE_DESCRIPTION("DCCP - Datagram Congestion Controlled Protocol");
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;
diff --git a/net/sctp/protocol.c b/net/sctp/protocol.c
index 8d3f8096b873..7d8ec6526347 100644
--- a/net/sctp/protocol.c
+++ b/net/sctp/protocol.c
@@ -1242,6 +1242,10 @@ SCTP_STATIC __exit void sctp_exit(void)
 module_init(sctp_init);
 module_exit(sctp_exit);
 
+/*
+ * __stringify doesn't likes enums, so use IPPROTO_SCTP value (132) directly.
+ */
+MODULE_ALIAS("net-pf-" __stringify(PF_INET) "-proto-132");
 MODULE_AUTHOR("Linux Kernel SCTP developers <lksctp-developers@lists.sourceforge.net>");
 MODULE_DESCRIPTION("Support for the SCTP protocol (RFC2960)");
 MODULE_LICENSE("GPL");