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>

1 files changed, 56 insertions, 17 deletions

diff --git a/net/iucv/af_iucv.c b/net/iucv/af_iucv.c
index 47c5c8d3703f..95e38d3d2d74 100644
--- 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);