af_iucv: New socket option for setting IUCV MSGLIMITs

The SO_MSGLIMIT socket option modifies the message limit for new
IUCV communication paths.

The message limit specifies the maximum number of outstanding messages
that are allowed for connections. This setting can be lowered by z/VM
when an IUCV connection is established.

Expects an integer value in the range of 1 to 65535.
The default value is 65535.

The message limit must be set before calling connect() or listen()
for sockets.

If sockets are already connected or in state listen, changing the message
limit is not supported.
For reading the message limit value, unconnected sockets return the limit
that has been set or the default limit. For connected sockets, the actual
message limit is returned. The actual message limit is assigned by z/VM
for each connection and it depends on IUCV MSGLIMIT authorizations
specified for the z/VM guest virtual machine.

Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Signed-off-by: Ursula Braun <ursula.braun@de.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/net/iucv/af_iucv.h b/include/net/iucv/af_iucv.h
index b57739e49dc1..21ee49ffcbaf 100644
--- a/include/net/iucv/af_iucv.h
+++ b/include/net/iucv/af_iucv.h
@@ -74,10 +74,12 @@ struct iucv_sock {
         struct sock_msg_q       message_q;
         unsigned int            send_tag;
         u8                      flags;
+        u16                     msglimit;
 };
 
 /* iucv socket options (SOL_IUCV) */
 #define SO_IPRMDATA_MSG 0x0080          /* send/recv IPRM_DATA msgs */
+#define SO_MSGLIMIT     0x1000          /* get/set IUCV MSGLIMIT */
 
 /* iucv related control messages (scm) */
 #define SCM_IUCV_TRGCLS 0x0001          /* target class control message */