CAPI: Rework capiminor RX handler

Avoid re-queuing skbs unless the error detected in handle_recv_skb is
expected to be recoverable such as lacking memory, a full CAPI queue, a
full TTY input buffer, or a not yet existing TTY.

Signed-off-by: Jan Kiszka <jan.kiszka@web.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/isdn/capi/capi.c b/drivers/isdn/capi/capi.c
index 554fa1b..c5c54fa 100644 (file)
--- a/drivers/isdn/capi/capi.c
+++ b/drivers/isdn/capi/capi.c
@@ -436,15 +436,13 @@ gen_data_b3_resp_for(struct capiminor *mp, struct sk_buff *skb)
 
 static int handle_recv_skb(struct capiminor *mp, struct sk_buff *skb)
 {
+       unsigned int datalen = skb->len - CAPIMSG_LEN(skb->data);
        struct tty_struct *tty;
        struct sk_buff *nskb;
-       int datalen;
        u16 errcode, datahandle;
        struct tty_ldisc *ld;
        int ret = -1;
 
-       datalen = skb->len - CAPIMSG_LEN(skb->data);
-
        tty = tty_port_tty_get(&mp->port);
        if (!tty) {
 #ifdef _DEBUG_DATAFLOW
@@ -454,50 +452,68 @@ static int handle_recv_skb(struct capiminor *mp, struct sk_buff *skb)
        }
        
        ld = tty_ldisc_ref(tty);
-       if (!ld)
-               goto out1;
+       if (!ld) {
+               /* fatal error, do not requeue */
+               ret = 0;
+               kfree_skb(skb);
+               goto deref_tty;
+       }
 
        if (ld->ops->receive_buf == NULL) {
 #if defined(_DEBUG_DATAFLOW) || defined(_DEBUG_TTYFUNCS)
                printk(KERN_DEBUG "capi: ldisc has no receive_buf function\n");
 #endif
-               goto out2;
+               /* fatal error, do not requeue */
+               goto free_skb;
        }
        if (mp->ttyinstop) {
 #if defined(_DEBUG_DATAFLOW) || defined(_DEBUG_TTYFUNCS)
                printk(KERN_DEBUG "capi: recv tty throttled\n");
 #endif
-               goto out2;
+               goto deref_ldisc;
        }
+
        if (tty->receive_room < datalen) {
 #if defined(_DEBUG_DATAFLOW) || defined(_DEBUG_TTYFUNCS)
                printk(KERN_DEBUG "capi: no room in tty\n");
 #endif
-               goto out2;
+               goto deref_ldisc;
        }
-       if ((nskb = gen_data_b3_resp_for(mp, skb)) == NULL) {
+
+       nskb = gen_data_b3_resp_for(mp, skb);
+       if (!nskb) {
                printk(KERN_ERR "capi: gen_data_b3_resp failed\n");
-               goto out2;
+               goto deref_ldisc;
        }
-       datahandle = CAPIMSG_U16(skb->data,CAPIMSG_BASELEN+4);
+
+       datahandle = CAPIMSG_U16(skb->data, CAPIMSG_BASELEN + 4);
+
        errcode = capi20_put_message(mp->ap, nskb);
-       if (errcode != CAPI_NOERROR) {
+
+       if (errcode == CAPI_NOERROR) {
+               skb_pull(skb, CAPIMSG_LEN(skb->data));
+#ifdef _DEBUG_DATAFLOW
+               printk(KERN_DEBUG "capi: DATA_B3_RESP %u len=%d => ldisc\n",
+                                       datahandle, skb->len);
+#endif
+               ld->ops->receive_buf(tty, skb->data, NULL, skb->len);
+       } else {
                printk(KERN_ERR "capi: send DATA_B3_RESP failed=%x\n",
                                errcode);
                kfree_skb(nskb);
-               goto out2;
+
+               if (errcode == CAPI_SENDQUEUEFULL)
+                       goto deref_ldisc;
        }
-       (void)skb_pull(skb, CAPIMSG_LEN(skb->data));
-#ifdef _DEBUG_DATAFLOW
-       printk(KERN_DEBUG "capi: DATA_B3_RESP %u len=%d => ldisc\n",
-                               datahandle, skb->len);
-#endif
-       ld->ops->receive_buf(tty, skb->data, NULL, skb->len);
-       kfree_skb(skb);
+
+free_skb:
        ret = 0;
-out2:
+       kfree_skb(skb);
+
+deref_ldisc:
        tty_ldisc_deref(ld);
-out1:
+
+deref_tty:
        tty_kref_put(tty);
        return ret;
 }