af_iucv: allow retrieval of maximum message size

For HS transport the maximum message size depends on the MTU-size
of the HS-device bound to the AF_IUCV socket. This patch adds a
getsockopt option MSGSIZE returning the maximum message size that
can be handled for this AF_IUCV socket.

Signed-off-by: Ursula Braun <ursula.braun@de.ibm.com>
Signed-off-by: Frank Blaschka <frank.blaschka@de.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 10 insertions, 1 deletions

diff --git a/include/net/iucv/af_iucv.h b/include/net/iucv/af_iucv.h
index a1517887aea..2e1d5ecc2d1 100644
--- a/include/net/iucv/af_iucv.h
+++ b/include/net/iucv/af_iucv.h
@@ -132,6 +132,7 @@ struct iucv_sock {
 /* iucv socket options (SOL_IUCV) */
 #define SO_IPRMDATA_MSG 0x0080          /* send/recv IPRM_DATA msgs */
 #define SO_MSGLIMIT     0x1000          /* get/set IUCV MSGLIMIT */
+#define SO_MSGSIZE      0x0800          /* get maximum msgsize */
 
 /* iucv related control messages (scm) */
 #define SCM_IUCV_TRGCLS 0x0001          /* target class control message */
diff --git a/net/iucv/af_iucv.c b/net/iucv/af_iucv.c
index fbce4a3126d..98d1f0ba7fe 100644
--- a/net/iucv/af_iucv.c
+++ b/net/iucv/af_iucv.c
@@ -1633,7 +1633,8 @@ static int iucv_sock_getsockopt(struct socket *sock, int level, int optname,
 {
         struct sock *sk = sock->sk;
         struct iucv_sock *iucv = iucv_sk(sk);
-        int val, len;
+        unsigned int val;
+        int len;
 
         if (level != SOL_IUCV)
                 return -ENOPROTOOPT;
@@ -1656,6 +1657,13 @@ static int iucv_sock_getsockopt(struct socket *sock, int level, int optname,
                                            : iucv->msglimit;    /* default */
                 release_sock(sk);
                 break;
+        case SO_MSGSIZE:
+                if (sk->sk_state == IUCV_OPEN)
+                        return -EBADFD;
+                val = (iucv->hs_dev) ? iucv->hs_dev->mtu -
+                                sizeof(struct af_iucv_trans_hdr) - ETH_HLEN :
+                                0x7fffffff;
+                break;
         default:
                 return -ENOPROTOOPT;
         }