[SCTP] Allow private to global association.

The sctp scoping rules try to prevent accidentally sending
non-routable addresses to a peer as alternate addresses.  However,
the current implementation is way too strict in that one can't
even try to send from a private address to a global address (a
pretty common real world setup with host behind NAT) even 
when that's the _only_ address available.

If we find no addresses available, try looking for a private address 
to send with, as a fallback.  
Additionally, if we are sending with only a single address, don't
bother embedding this address in the INIT/INIT-ACK chunk.  

net/sctp/bind_addr.c

@@ -80,6 +80,22 @@ int sctp_bind_addr_copy(sctp_bind_addr_t *dest, const sctp_bind_addr_t *src,
 			goto out;
 	}
 
+	/* If there are no addresses matching the scope and
+	 * this is global scope, try to get a link scope address, with
+	 * the assumption that we must be sitting behind a NAT.
+	 */
+	if (list_empty(&dest->address_list) && (SCTP_SCOPE_GLOBAL == scope)) {
+		list_for_each(pos, &src->address_list) {
+			addr = list_entry(pos, struct sockaddr_storage_list,
+					  list);
+			error = sctp_copy_one_addr(dest, &addr->a,
+						   SCTP_SCOPE_LINK, gfp,
+						   flags);
+			if (error < 0)
+				goto out;
+		}
+	}
+
 out:
 	if (error)
 		sctp_bind_addr_clean(dest);
@@ -214,6 +230,14 @@ union sctp_params sctp_bind_addrs_to_raw(const sctp_bind_addr_t *bp,
 		len += sizeof(sctp_addr_param_t);
 	}
 
+	/* Don't even bother embedding an address if there
+	 * is only one.
+	 */
+	if (len == sizeof(sctp_addr_param_t)) {
+		retval.v = NULL;
+		goto end_raw;
+	}
+
 	retval.v = kmalloc(len, gfp);
 	if (!retval.v)
 		goto end_raw;

net/sctp/sm_make_chunk.c

@@ -177,12 +177,9 @@ sctp_chunk_t *sctp_make_init(const struct sctp_association *asoc,
 	 * can be IPv4 and/or IPv6 in any combination.
 	 */
 	retval = NULL;
-	addrs.v = NULL;
 
-	/* Convert the provided bind address list to raw format */
+	/* Convert the provided bind address list to raw format. */
 	addrs = sctp_bind_addrs_to_raw(bp, &addrs_len, gfp);
-	if (!addrs.v)
-		goto nodata;
 
 	init.init_tag		   = htonl(asoc->c.my_vtag);
 	init.a_rwnd		   = htonl(asoc->rwnd);
@@ -252,9 +249,8 @@ sctp_chunk_t *sctp_make_init_ack(const struct sctp_association *asoc,
 
 	retval = NULL;
 
+	/* Note: there may be no addresses to embed. */
 	addrs = sctp_bind_addrs_to_raw(&asoc->base.bind_addr, &addrs_len, gfp);
-	if (!addrs.v)
-		goto nomem_rawaddr;
 
 	initack.init_tag	        = htonl(asoc->c.my_vtag);
 	initack.a_rwnd			= htonl(asoc->rwnd);
@@ -313,8 +309,8 @@ sctp_chunk_t *sctp_make_init_ack(const struct sctp_association *asoc,
 nomem_chunk:
 	kfree(cookie);
 nomem_cookie:
+	if (addrs.v)
 		kfree(addrs.v);
-nomem_rawaddr:
 	return retval;
 }
 
@@ -840,7 +836,7 @@ sctp_chunk_t *sctp_make_abort_user(const struct sctp_association *asoc,
 		payoff = payload;
 
 		for (; iovlen > 0; --iovlen) {
-			if (copy_from_user(payoff, iov->iov_base, iov->iov_len))
+			if (copy_from_user(payoff, iov->iov_base,iov->iov_len))
 				goto err_copy;
 			payoff += iov->iov_len;
 			iov++;
@@ -1542,6 +1538,12 @@ struct sctp_association *sctp_unpack_cookie(
 		goto fail;
 	}
 
+	/* Also, add the destination address. */
+	if (list_empty(&retval->base.bind_addr.address_list)) {
+		sctp_add_bind_addr(&retval->base.bind_addr, &chunk->dest, 
+				   GFP_ATOMIC);
+	}
+
 	retval->next_tsn = retval->c.initial_tsn;
 	retval->ctsn_ack_point = retval->next_tsn - 1;