diff --git a/net/arp.c b/net/arp.c
index 5ed875c..e58a074 100644
--- a/net/arp.c
+++ b/net/arp.c
@@ -52,12 +52,14 @@ void ArpRequest(void)
 {
 	uchar *pkt;
 	struct arp_hdr *arp;
+	int eth_hdr_size;
 
 	debug("ARP broadcast %d\n", NetArpWaitTry);
 
 	pkt = NetTxPacket;
 
-	pkt += NetSetEther(pkt, NetBcastAddr, PROT_ARP);
+	eth_hdr_size = NetSetEther(pkt, NetBcastAddr, PROT_ARP);
+	pkt += eth_hdr_size;
 
 	arp = (struct arp_hdr *) pkt;
 
@@ -86,7 +88,7 @@ void ArpRequest(void)
 	}
 
 	NetWriteIP(&arp->ar_tpa, NetArpWaitReplyIP);
-	(void) eth_send(NetTxPacket, (pkt - NetTxPacket) + ARP_HDR_SIZE);
+	(void) eth_send(NetTxPacket, eth_hdr_size + ARP_HDR_SIZE);
 }
 
 void ArpTimeoutCheck(void)
@@ -118,6 +120,7 @@ void ArpReceive(struct ethernet_hdr *et, struct ip_udp_hdr *ip, int len)
 	struct arp_hdr *arp;
 	IPaddr_t reply_ip_addr;
 	uchar *pkt;
+	int eth_hdr_size;
 
 	/*
 	 * We have to deal with two types of ARP packets:
@@ -155,14 +158,14 @@ void ArpReceive(struct ethernet_hdr *et, struct ip_udp_hdr *ip, int len)
 		/* reply with our IP address */
 		debug("Got ARP REQUEST, return our IP\n");
 		pkt = (uchar *)et;
-		pkt += NetSetEther(pkt, et->et_src, PROT_ARP);
+		eth_hdr_size = NetSetEther(pkt, et->et_src, PROT_ARP);
+		pkt += eth_hdr_size;
 		arp->ar_op = htons(ARPOP_REPLY);
 		memcpy(&arp->ar_tha, &arp->ar_sha, ARP_HLEN);
 		NetCopyIP(&arp->ar_tpa, &arp->ar_spa);
 		memcpy(&arp->ar_sha, NetOurEther, ARP_HLEN);
 		NetCopyIP(&arp->ar_spa, &NetOurIP);
-		(void) eth_send((uchar *)et,
-				(pkt - (uchar *)et) + ARP_HDR_SIZE);
+		(void) eth_send((uchar *)et, eth_hdr_size + ARP_HDR_SIZE);
 		return;
 
 	case ARPOP_REPLY:		/* arp reply */
diff --git a/net/ping.c b/net/ping.c
index c525635..939f8ff 100644
--- a/net/ping.c
+++ b/net/ping.c
@@ -42,6 +42,7 @@ static int ping_send(void)
 {
 	static uchar mac[6];
 	uchar *pkt;
+	int eth_hdr_size;
 
 	/* XXX always send arp request */
 
@@ -53,13 +54,13 @@ static int ping_send(void)
 	NetArpWaitPacketMAC = mac;
 
 	pkt = NetArpWaitTxPacket;
-	pkt += NetSetEther(pkt, mac, PROT_IP);
+	eth_hdr_size = NetSetEther(pkt, mac, PROT_IP);
+	pkt += eth_hdr_size;
 
 	set_icmp_header(pkt, NetPingIP);
 
 	/* size of the waiting packet */
-	NetArpWaitTxPacketSize =
-		(pkt - NetArpWaitTxPacket) + IP_HDR_SIZE + 8;
+	NetArpWaitTxPacketSize = eth_hdr_size + IP_ICMP_HDR_SIZE;
 
 	/* and do the ARP request */
 	NetArpWaitTry = 1;
diff --git a/net/rarp.c b/net/rarp.c
index da50961..a715c2c 100644
--- a/net/rarp.c
+++ b/net/rarp.c
@@ -88,11 +88,13 @@ void RarpRequest(void)
 {
 	uchar *pkt;
 	struct arp_hdr *rarp;
+	int eth_hdr_size;
 
 	printf("RARP broadcast %d\n", ++RarpTry);
 	pkt = NetTxPacket;
 
-	pkt += NetSetEther(pkt, NetBcastAddr, PROT_RARP);
+	eth_hdr_size = NetSetEther(pkt, NetBcastAddr, PROT_RARP);
+	pkt += eth_hdr_size;
 
 	rarp = (struct arp_hdr *)pkt;
 
@@ -108,7 +110,7 @@ void RarpRequest(void)
 	/* dest IP addr set to broadcast */
 	memset(&rarp->ar_data[16], 0xff,        4);
 
-	NetSendPacket(NetTxPacket, (pkt - NetTxPacket) + ARP_HDR_SIZE);
+	NetSendPacket(NetTxPacket, eth_hdr_size + ARP_HDR_SIZE);
 
 	NetSetTimeout(TIMEOUT, RarpTimeout);
 }