slirp: Refactor if_start

Replace gotos with a while loop, fix coding style.

CC: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
CC: Fabien Chouteau <chouteau@adacore.com>
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
diff --git a/slirp/if.c b/slirp/if.c
index 710ec23..33f08e1 100644
--- a/slirp/if.c
+++ b/slirp/if.c
@@ -149,39 +149,36 @@
  * from the second session, then one packet from the third, then back
  * to the first, etc. etc.
  */
-void
-if_start(Slirp *slirp)
+void if_start(Slirp *slirp)
 {
     uint64_t now = qemu_get_clock_ns(rt_clock);
     int requeued = 0;
     bool from_batchq = false;
-	struct mbuf *ifm, *ifqt;
+    struct mbuf *ifm, *ifqt;
 
-	DEBUG_CALL("if_start");
+    DEBUG_CALL("if_start");
 
-	if (slirp->if_queued == 0)
-	   return; /* Nothing to do */
-
- again:
+    while (slirp->if_queued) {
         /* check if we can really output */
         if (!slirp_can_output(slirp->opaque))
             return;
 
-	/*
-	 * See which queue to get next packet from
-	 * If there's something in the fastq, select it immediately
-	 */
-	if (slirp->if_fastq.ifq_next != &slirp->if_fastq) {
-		ifm = slirp->if_fastq.ifq_next;
-	} else {
-		/* Nothing on fastq, see if next_m is valid */
-		if (slirp->next_m != &slirp->if_batchq)
-		   ifm = slirp->next_m;
-		else
-		   ifm = slirp->if_batchq.ifq_next;
+        /*
+         * See which queue to get next packet from
+         * If there's something in the fastq, select it immediately
+         */
+        if (slirp->if_fastq.ifq_next != &slirp->if_fastq) {
+            ifm = slirp->if_fastq.ifq_next;
+        } else {
+            /* Nothing on fastq, see if next_m is valid */
+            if (slirp->next_m != &slirp->if_batchq) {
+                ifm = slirp->next_m;
+            } else {
+                ifm = slirp->if_batchq.ifq_next;
+            }
 
-                from_batchq = true;
-	}
+            from_batchq = true;
+        }
 
         slirp->if_queued--;
 
@@ -189,7 +186,7 @@
         if (ifm->expiration_date >= now && !if_encap(slirp, ifm)) {
             /* Packet is delayed due to pending ARP resolution */
             requeued++;
-            goto out;
+            continue;
         }
 
         if (from_batchq) {
@@ -197,28 +194,25 @@
             slirp->next_m = ifm->ifq_next;
         }
 
-	/* Remove it from the queue */
-	ifqt = ifm->ifq_prev;
-	remque(ifm);
+        /* Remove it from the queue */
+        ifqt = ifm->ifq_prev;
+        remque(ifm);
 
-	/* If there are more packets for this session, re-queue them */
-	if (ifm->ifs_next != /* ifm->ifs_prev != */ ifm) {
-		insque(ifm->ifs_next, ifqt);
-		ifs_remque(ifm);
-	}
+        /* If there are more packets for this session, re-queue them */
+        if (ifm->ifs_next != ifm) {
+            insque(ifm->ifs_next, ifqt);
+            ifs_remque(ifm);
+        }
 
-	/* Update so_queued */
-	if (ifm->ifq_so) {
-		if (--ifm->ifq_so->so_queued == 0)
-		   /* If there's no more queued, reset nqueued */
-		   ifm->ifq_so->so_nqueued = 0;
-	}
+        /* Update so_queued */
+        if (ifm->ifq_so && --ifm->ifq_so->so_queued == 0) {
+            /* If there's no more queued, reset nqueued */
+            ifm->ifq_so->so_nqueued = 0;
+        }
 
         m_free(ifm);
 
- out:
-	if (slirp->if_queued)
-	   goto again;
+    }
 
-        slirp->if_queued = requeued;
+    slirp->if_queued = requeued;
 }