af_iucv: Provide new socket type SOCK_SEQPACKET

This patch provides the socket type SOCK_SEQPACKET in addition to
SOCK_STREAM.

AF_IUCV sockets of type SOCK_SEQPACKET supports an 1:1 mapping of
socket read or write operations to complete IUCV messages.
Socket data or IUCV message data is not fragmented as this is the
case for SOCK_STREAM sockets.

The intention is to help application developers who write
applications or device drivers using native IUCV interfaces
(Linux kernel or z/VM IUCV interfaces).

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>

diff --git a/net/iucv/af_iucv.c b/net/iucv/af_iucv.c
index 47c5c8d..95e38d3 100644 (file)
--- a/net/iucv/af_iucv.c
+++ b/net/iucv/af_iucv.c
@@ -289,11 +289,22 @@ static int iucv_sock_create(struct net *net, struct socket *sock, int protocol)
 {
        struct sock *sk;
 
-       if (sock->type != SOCK_STREAM)
-               return -ESOCKTNOSUPPORT;
+       if (protocol && protocol != PF_IUCV)
+               return -EPROTONOSUPPORT;
 
        sock->state = SS_UNCONNECTED;
-       sock->ops = &iucv_sock_ops;
+
+       switch (sock->type) {
+       case SOCK_STREAM:
+               sock->ops = &iucv_sock_ops;
+               break;
+       case SOCK_SEQPACKET:
+               /* currently, proto ops can handle both sk types */
+               sock->ops = &iucv_sock_ops;
+               break;
+       default:
+               return -ESOCKTNOSUPPORT;
+       }
 
        sk = iucv_sock_alloc(sock, protocol, GFP_KERNEL);
        if (!sk)
@@ -504,11 +515,9 @@ static int iucv_sock_connect(struct socket *sock, struct sockaddr *addr,
        if (sk->sk_state != IUCV_OPEN && sk->sk_state != IUCV_BOUND)
                return -EBADFD;
 
-       if (sk->sk_type != SOCK_STREAM)
+       if (sk->sk_type != SOCK_STREAM && sk->sk_type != SOCK_SEQPACKET)
                return -EINVAL;
 
-       iucv = iucv_sk(sk);
-
        if (sk->sk_state == IUCV_OPEN) {
                err = iucv_sock_autobind(sk);
                if (unlikely(err))
@@ -585,7 +594,10 @@ static int iucv_sock_listen(struct socket *sock, int backlog)
        lock_sock(sk);
 
        err = -EINVAL;
-       if (sk->sk_state != IUCV_BOUND || sock->type != SOCK_STREAM)
+       if (sk->sk_state != IUCV_BOUND)
+               goto done;
+
+       if (sock->type != SOCK_STREAM && sock->type != SOCK_SEQPACKET)
                goto done;
 
        sk->sk_max_ack_backlog = backlog;
@@ -720,6 +732,10 @@ static int iucv_sock_sendmsg(struct kiocb *iocb, struct socket *sock,
        if (msg->msg_flags & MSG_OOB)
                return -EOPNOTSUPP;
 
+       /* SOCK_SEQPACKET: we do not support segmented records */
+       if (sk->sk_type == SOCK_SEQPACKET && !(msg->msg_flags & MSG_EOR))
+               return -EOPNOTSUPP;
+
        lock_sock(sk);
 
        if (sk->sk_shutdown & SEND_SHUTDOWN) {
@@ -770,6 +786,10 @@ static int iucv_sock_sendmsg(struct kiocb *iocb, struct socket *sock,
                        }
                }
 
+               /* allocate one skb for each iucv message:
+                * this is fine for SOCK_SEQPACKET (unless we want to support
+                * segmented records using the MSG_EOR flag), but
+                * for SOCK_STREAM we might want to improve it in future */
                if (!(skb = sock_alloc_send_skb(sk, len,
                                                msg->msg_flags & MSG_DONTWAIT,
                                                &err)))
@@ -897,7 +917,11 @@ static void iucv_process_message(struct sock *sk, struct sk_buff *skb,
                        kfree_skb(skb);
                        return;
                }
-               if (skb->truesize >= sk->sk_rcvbuf / 4) {
+               /* we need to fragment iucv messages for SOCK_STREAM only;
+                * for SOCK_SEQPACKET, it is only relevant if we support
+                * record segmentation using MSG_EOR (see also recvmsg()) */
+               if (sk->sk_type == SOCK_STREAM &&
+                   skb->truesize >= sk->sk_rcvbuf / 4) {
                        rc = iucv_fragment_skb(sk, skb, len);
                        kfree_skb(skb);
                        skb = NULL;
@@ -941,7 +965,8 @@ static int iucv_sock_recvmsg(struct kiocb *iocb, struct socket *sock,
        int noblock = flags & MSG_DONTWAIT;
        struct sock *sk = sock->sk;
        struct iucv_sock *iucv = iucv_sk(sk);
-       int target, copied = 0;
+       int target;
+       unsigned int copied, rlen;
        struct sk_buff *skb, *rskb, *cskb;
        int err = 0;
 
@@ -963,7 +988,8 @@ static int iucv_sock_recvmsg(struct kiocb *iocb, struct socket *sock,
                return err;
        }
 
-       copied = min_t(unsigned int, skb->len, len);
+       rlen   = skb->len;              /* real length of skb */
+       copied = min_t(unsigned int, rlen, len);
 
        cskb = skb;
        if (memcpy_toiovec(msg->msg_iov, cskb->data, copied)) {
@@ -973,7 +999,13 @@ static int iucv_sock_recvmsg(struct kiocb *iocb, struct socket *sock,
                goto done;
        }
 
-       len -= copied;
+       /* SOCK_SEQPACKET: set MSG_TRUNC if recv buf size is too small */
+       if (sk->sk_type == SOCK_SEQPACKET) {
+               if (copied < rlen)
+                       msg->msg_flags |= MSG_TRUNC;
+               /* each iucv message contains a complete record */
+               msg->msg_flags |= MSG_EOR;
+       }
 
        /* create control message to store iucv msg target class:
         * get the trgcls from the control buffer of the skb due to
@@ -988,11 +1020,14 @@ static int iucv_sock_recvmsg(struct kiocb *iocb, struct socket *sock,
 
        /* Mark read part of skb as used */
        if (!(flags & MSG_PEEK)) {
-               skb_pull(skb, copied);
 
-               if (skb->len) {
-                       skb_queue_head(&sk->sk_receive_queue, skb);
-                       goto done;
+               /* SOCK_STREAM: re-queue skb if it contains unreceived data */
+               if (sk->sk_type == SOCK_STREAM) {
+                       skb_pull(skb, copied);
+                       if (skb->len) {
+                               skb_queue_head(&sk->sk_receive_queue, skb);
+                               goto done;
+                       }
                }
 
                kfree_skb(skb);
@@ -1019,7 +1054,11 @@ static int iucv_sock_recvmsg(struct kiocb *iocb, struct socket *sock,
                skb_queue_head(&sk->sk_receive_queue, skb);
 
 done:
-       return err ? : copied;
+       /* SOCK_SEQPACKET: return real length if MSG_TRUNC is set */
+       if (sk->sk_type == SOCK_SEQPACKET && (flags & MSG_TRUNC))
+               copied = rlen;
+
+       return copied;
 }
 
 static inline unsigned int iucv_accept_poll(struct sock *parent)
@@ -1281,7 +1320,7 @@ static int iucv_callback_connreq(struct iucv_path *path,
        }
 
        /* Create the new socket */
-       nsk = iucv_sock_alloc(NULL, SOCK_STREAM, GFP_ATOMIC);
+       nsk = iucv_sock_alloc(NULL, sk->sk_type, GFP_ATOMIC);
        if (!nsk) {
                err = iucv_path_sever(path, user_data);
                iucv_path_free(path);