tipc: let function tipc_msg_reverse() expand header when needed

The shortest TIPC message header, for cluster local CONNECTED messages,
is 24 bytes long. With this format, the fields "dest_node" and
"orig_node" are optimized away, since they in reality are redundant
in this particular case.

However, the absence of these fields leads to code inconsistencies
that are difficult to handle in some cases, especially when we need
to reverse or reject messages at the socket layer.

In this commit, we concentrate the handling of the absent fields
to one place, by letting the function tipc_msg_reverse() reallocate
the buffer and expand the header to 32 bytes when necessary. This
means that the socket code now can assume that the two previously
absent fields are present in the header when a message needs to be
rejected. This opens up for some further simplifications of the
socket code.

Reviewed-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 1 insertions, 2 deletions

diff --git a/net/tipc/msg.h b/net/tipc/msg.h
index 2f1563b47e24..0e96f59e3315 100644
--- a/net/tipc/msg.h
+++ b/net/tipc/msg.h
@@ -785,8 +785,7 @@ static inline bool msg_peer_is_up(struct tipc_msg *m)
 
 struct sk_buff *tipc_buf_acquire(u32 size);
 bool tipc_msg_validate(struct sk_buff *skb);
-bool tipc_msg_reverse(u32 own_addr, struct sk_buff *buf, u32 *dnode,
-		      int err);
+bool tipc_msg_reverse(u32 own_addr, struct sk_buff **skb, u32 *dnode, int err);
 void tipc_msg_init(u32 own_addr, struct tipc_msg *m, u32 user, u32 type,
 		   u32 hsize, u32 destnode);
 struct sk_buff *tipc_msg_create(uint user, uint type, uint hdr_sz,