Dave, Alexey,
I think i found a bug in inet_register_protosw() which results in a behavior
that is not expected.
Registering a new protocol of type SOCK_STREAM with a protocol value other
than IPPROTO_TCP will override TCP if the application passes 0 as the protocol
to the socket() call.
socket(AF_INET, SOCK_STREAM, 0)
I guess many applications follow this syntax as they assume TCP is the default
protocol for SOCK_STREAM type.
The same holds true for SOCK_DGRAM type sockets assuing UDP as the default.
This is due to the insertion of a new inet_protosw entry into the inetsw list
of a particular type at the head of the list. inet_create() uses the first
entry in the list if a wild-card protocol is passed.
The following patch fixes the insertion of a new entry so that it is added
after the last permanent entry in the list. This makes sure that the new
entries do not override any existing permanent entries.
I found this problem when i registered SOCK_STREAM/IPPROTO_SCTP to support
tcp-style SCTP sockets and surprisingly noticed 'ssh' using SCTP as the
transport protocol.
Thanks
Sridhar
Patch against linux 2.5.62
-------------------------------------------------------------------------------
diff -Nru a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
--- a/net/ipv4/af_inet.c Wed Feb 19 15:37:34 2003
+++ b/net/ipv4/af_inet.c Wed Feb 19 15:37:34 2003
@@ -976,6 +976,7 @@
struct list_head *lh;
struct inet_protosw *answer;
int protocol = p->protocol;
+ struct list_head *last_perm;
br_write_lock_bh(BR_NETPROTO_LOCK);
@@ -984,24 +985,29 @@
/* If we are trying to override a permanent protocol, bail. */
answer = NULL;
+ last_perm = &inetsw[p->type];
list_for_each(lh, &inetsw[p->type]) {
answer = list_entry(lh, struct inet_protosw, list);
/* Check only the non-wild match. */
- if (protocol == answer->protocol &&
- (INET_PROTOSW_PERMANENT & answer->flags))
- break;
+ if (INET_PROTOSW_PERMANENT & answer->flags) {
+ if (protocol == answer->protocol)
+ break;
+ last_perm = lh;
+ }
answer = NULL;
}
if (answer)
goto out_permanent;
- /* Add to the BEGINNING so that we override any existing
- * entry. This means that when we remove this entry, the
+ /* Add the new entry after the last permanent entry if any, so that
+ * the new entry does not override a permanent entry when matched with
+ * a wild-card protocol. But it is allowed to override any existing
+ * non-permanent entry. This means that when we remove this entry, the
* system automatically returns to the old behavior.
*/
- list_add(&p->list, &inetsw[p->type]);
+ list_add(&p->list, last_perm);
out:
br_write_unlock_bh(BR_NETPROTO_LOCK);
return;
diff -Nru a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
--- a/net/ipv6/af_inet6.c Wed Feb 19 15:37:34 2003
+++ b/net/ipv6/af_inet6.c Wed Feb 19 15:37:34 2003
@@ -571,6 +571,7 @@
struct list_head *lh;
struct inet_protosw *answer;
int protocol = p->protocol;
+ struct list_head *last_perm;
br_write_lock_bh(BR_NETPROTO_LOCK);
@@ -579,24 +580,29 @@
/* If we are trying to override a permanent protocol, bail. */
answer = NULL;
+ last_perm = &inetsw6[p->type];
list_for_each(lh, &inetsw6[p->type]) {
answer = list_entry(lh, struct inet_protosw, list);
/* Check only the non-wild match. */
- if (protocol == answer->protocol &&
- (INET_PROTOSW_PERMANENT & answer->flags))
- break;
+ if (INET_PROTOSW_PERMANENT & answer->flags) {
+ if (protocol == answer->protocol)
+ break;
+ last_perm = lh;
+ }
answer = NULL;
}
if (answer)
goto out_permanent;
- /* Add to the BEGINNING so that we override any existing
- * entry. This means that when we remove this entry, the
+ /* Add the new entry after the last permanent entry if any, so that
+ * the new entry does not override a permanent entry when matched with
+ * a wild-card protocol. But it is allowed to override any existing
+ * non-permanent entry. This means that when we remove this entry, the
* system automatically returns to the old behavior.
*/
- list_add(&p->list, &inetsw6[p->type]);
+ list_add(&p->list, last_perm);
out:
br_write_unlock_bh(BR_NETPROTO_LOCK);
return;
-
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