net/arp: account for ARP delay, avoid duplicate packets on timeout

eth_rx() in the main reception loop may trigger sending a packet which
is already timed out (or will immediately) upon reception of an ARP reply.
As long as the ARP reply is pending, the timeout handler of a packet
should be postponed.
Happens on TFTP with bad network (e.g. WLAN).

Signed-off-by: Stefan Brüns <stefan.bruens@rwth-aachen.de>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>

net/arp.c

@@ -96,12 +96,12 @@ void arp_request(void)
 	arp_raw_request(net_ip, net_null_ethaddr, net_arp_wait_reply_ip);
 }
 
-void arp_timeout_check(void)
+int arp_timeout_check(void)
 {
 	ulong t;
 
 	if (!net_arp_wait_packet_ip.s_addr)
-		return;
+		return 0;
 
 	t = get_timer(0);
 
@@ -118,6 +118,7 @@ void arp_timeout_check(void)
 			arp_request();
 		}
 	}
+	return 1;
 }
 
 void arp_receive(struct ethernet_hdr *et, struct ip_udp_hdr *ip, int len)

net/arp.h

@@ -25,7 +25,7 @@ void arp_init(void);
 void arp_request(void);
 void arp_raw_request(struct in_addr source_ip, const uchar *targetEther,
 	struct in_addr target_ip);
-void arp_timeout_check(void);
+int arp_timeout_check(void);
 void arp_receive(struct ethernet_hdr *et, struct ip_udp_hdr *ip, int len);
 
 #endif /* __ARP_H__ */

net/net.c

@@ -569,7 +569,9 @@ restart:
 			goto done;
 		}
 
-		arp_timeout_check();
+		if (arp_timeout_check() > 0) {
+		    time_start = get_timer(0);
+		}
 
 		/*
 		 *	Check for a timeout, and run the timeout handler