af_iucv: Modify iucv msg target class using control msghdr

Allow 'classification' of socket data that is sent or received over
an af_iucv socket. For classification of data, the target class of an
(native) iucv message is used.

This patch provides the cmsg interface for iucv_sock_recvmsg() and
iucv_sock_sendmsg().  Applications can use the msg_control field of
struct msghdr to set or get the target class as a
"socket control message" (SCM/CMSG).

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, 75 insertions, 4 deletions

diff --git a/net/iucv/af_iucv.c b/net/iucv/af_iucv.c
index 5fc077ee5831..47c5c8d3703f 100644
--- a/net/iucv/af_iucv.c
+++ b/net/iucv/af_iucv.c
@@ -45,6 +45,15 @@ static struct proto iucv_proto = {
 static const u8 iprm_shutdown[8] =
         {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01};
 
+#define TRGCLS_SIZE     (sizeof(((struct iucv_message *)0)->class))
+
+/* macros to set/get socket control buffer at correct offset */
+#define CB_TAG(skb)     ((skb)->cb)             /* iucv message tag */
+#define CB_TAG_LEN      (sizeof(((struct iucv_message *) 0)->tag))
+#define CB_TRGCLS(skb)  ((skb)->cb + CB_TAG_LEN) /* iucv msg target class */
+#define CB_TRGCLS_LEN   (TRGCLS_SIZE)
+
+
 static void iucv_sock_kill(struct sock *sk);
 static void iucv_sock_close(struct sock *sk);
 
@@ -698,6 +707,8 @@ static int iucv_sock_sendmsg(struct kiocb *iocb, struct socket *sock,
         struct iucv_sock *iucv = iucv_sk(sk);
         struct sk_buff *skb;
         struct iucv_message txmsg;
+        struct cmsghdr *cmsg;
+        int cmsg_done;
         char user_id[9];
         char appl_id[9];
         int err;
@@ -717,6 +728,48 @@ static int iucv_sock_sendmsg(struct kiocb *iocb, struct socket *sock,
         }
 
         if (sk->sk_state == IUCV_CONNECTED) {
+                /* initialize defaults */
+                cmsg_done   = 0;        /* check for duplicate headers */
+                txmsg.class = 0;
+
+                /* iterate over control messages */
+                for (cmsg = CMSG_FIRSTHDR(msg); cmsg;
+                     cmsg = CMSG_NXTHDR(msg, cmsg)) {
+
+                        if (!CMSG_OK(msg, cmsg)) {
+                                err = -EINVAL;
+                                goto out;
+                        }
+
+                        if (cmsg->cmsg_level != SOL_IUCV)
+                                continue;
+
+                        if (cmsg->cmsg_type & cmsg_done) {
+                                err = -EINVAL;
+                                goto out;
+                        }
+                        cmsg_done |= cmsg->cmsg_type;
+
+                        switch (cmsg->cmsg_type) {
+                        case SCM_IUCV_TRGCLS:
+                                if (cmsg->cmsg_len != CMSG_LEN(TRGCLS_SIZE)) {
+                                        err = -EINVAL;
+                                        goto out;
+                                }
+
+                                /* set iucv message target class */
+                                memcpy(&txmsg.class,
+                                        (void *) CMSG_DATA(cmsg), TRGCLS_SIZE);
+
+                                break;
+
+                        default:
+                                err = -EINVAL;
+                                goto out;
+                                break;
+                        }
+                }
+
                 if (!(skb = sock_alloc_send_skb(sk, len,
                                                 msg->msg_flags & MSG_DONTWAIT,
                                                 &err)))
@@ -727,10 +780,9 @@ static int iucv_sock_sendmsg(struct kiocb *iocb, struct socket *sock,
                         goto fail;
                 }
 
-                txmsg.class = 0;
-                memcpy(&txmsg.class, skb->data, skb->len >= 4 ? 4 : skb->len);
+                /* increment and save iucv message tag for msg_completion cbk */
                 txmsg.tag = iucv->send_tag++;
-                memcpy(skb->cb, &txmsg.tag, 4);
+                memcpy(CB_TAG(skb), &txmsg.tag, CB_TAG_LEN);
                 skb_queue_tail(&iucv->send_skb_q, skb);
 
                 if (((iucv->path->flags & IUCV_IPRMDATA) & iucv->flags)
@@ -801,6 +853,10 @@ static int iucv_fragment_skb(struct sock *sk, struct sk_buff *skb, int len)
                 if (!nskb)
                         return -ENOMEM;
 
+                /* copy target class to control buffer of new skb */
+                memcpy(CB_TRGCLS(nskb), CB_TRGCLS(skb), CB_TRGCLS_LEN);
+
+                /* copy data fragment */
                 memcpy(nskb->data, skb->data + copied, size);
                 copied += size;
                 dataleft -= size;
@@ -824,6 +880,10 @@ static void iucv_process_message(struct sock *sk, struct sk_buff *skb,
 
         len = iucv_msg_length(msg);
 
+        /* store msg target class in the second 4 bytes of skb ctrl buffer */
+        /* Note: the first 4 bytes are reserved for msg tag */
+        memcpy(CB_TRGCLS(skb), &msg->class, CB_TRGCLS_LEN);
+
         /* check for special IPRM messages (e.g. iucv_sock_shutdown) */
         if ((msg->flags & IUCV_IPRMDATA) && len > 7) {
                 if (memcmp(msg->rmmsg, iprm_shutdown, 8) == 0) {
@@ -915,6 +975,17 @@ static int iucv_sock_recvmsg(struct kiocb *iocb, struct socket *sock,
 
         len -= copied;
 
+        /* create control message to store iucv msg target class:
+         * get the trgcls from the control buffer of the skb due to
+         * fragmentation of original iucv message. */
+        err = put_cmsg(msg, SOL_IUCV, SCM_IUCV_TRGCLS,
+                        CB_TRGCLS_LEN, CB_TRGCLS(skb));
+        if (err) {
+                if (!(flags & MSG_PEEK))
+                        skb_queue_head(&sk->sk_receive_queue, skb);
+                return err;
+        }
+
         /* Mark read part of skb as used */
         if (!(flags & MSG_PEEK)) {
                 skb_pull(skb, copied);
@@ -1316,7 +1387,7 @@ static void iucv_callback_txdone(struct iucv_path *path,
                 spin_lock_irqsave(&list->lock, flags);
 
                 while (list_skb != (struct sk_buff *)list) {
-                        if (!memcmp(&msg->tag, list_skb->cb, 4)) {
+                        if (!memcmp(&msg->tag, CB_TAG(list_skb), CB_TAG_LEN)) {
                                 this = list_skb;
                                 break;
                         }