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>

1 files changed, 38 insertions, 22 deletions

diff --git a/drivers/isdn/capi/capi.c b/drivers/isdn/capi/capi.c
index 554fa1b36d13..c5c54fab50eb 100644
--- 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;
 }