diff --git a/src/include/gpxe/ip.h b/src/include/gpxe/ip.h
index 2212d8e5..e497dd79 100644
--- a/src/include/gpxe/ip.h
+++ b/src/include/gpxe/ip.h
@@ -11,7 +11,6 @@
 
 /* IP constants */
 
-#define IP_HLEN 	20
 #define IP_VER		4
 #define IP_MASK_VER	0xf0
 #define IP_MASK_HLEN 	0x0f
@@ -21,16 +20,20 @@
 #define IP_TOS		0
 #define IP_TTL		64
 
-/* IP6 constants */
-
-#define IP6_HLEN	38
+/* IP4 pseudo header */
+struct ipv4_pseudo_header {
+	struct in_addr src;
+	struct in_addr dest;
+	uint8_t zero_padding;
+	uint8_t protocol;
+	uint16_t len;
+};
 
 struct pk_buff;
 struct net_device;
 struct net_protocol;
 
 extern struct net_protocol ipv4_protocol;
-extern struct net_protocol ipv6_protocol;
 
 extern int add_ipv4_address ( struct net_device *netdev,
 			      struct in_addr address, struct in_addr netmask,
@@ -38,11 +41,6 @@ extern int add_ipv4_address ( struct net_device *netdev,
 extern void del_ipv4_address ( struct net_device *netdev );
 
 extern int ipv4_uip_tx ( struct pk_buff *pkb );
-
 extern int ipv4_tx ( struct pk_buff *pkb, uint16_t trans_proto, struct in_addr *dest );
-extern int ipv6_tx ( struct pk_buff *pkb, uint16_t trans_proto, struct in6_addr *dest );
-
-extern void ipv4_rx ( struct pk_buff *pkb, struct net_device *netdev, const void *ll_source );
-extern void ipv6_rx ( struct pk_buff *pkb, struct net_device *netdev, const void *ll_source );
 
 #endif /* _GPXE_IP_H */
diff --git a/src/net/ipv4.c b/src/net/ipv4.c
index 91b2d7ff..b770301a 100644
--- a/src/net/ipv4.c
+++ b/src/net/ipv4.c
@@ -124,21 +124,18 @@ static void ipv4_dump ( struct iphdr *iphdr __unused ) {
 void ipv4_tx_csum ( struct pk_buff *pkb, uint8_t trans_proto ) {
 
 	struct iphdr *iphdr = pkb->data;
-	void *pshdr = malloc ( IP_PSHLEN );
-	void *csum_offset = iphdr + IP_HLEN + ( trans_proto == IP_UDP ? 6 : 16 );
-	int offset = 0;
+	struct ipv4_pseudo_header pshdr;
+	void *csum_offset = iphdr + sizeof ( *iphdr ) + ( trans_proto == IP_UDP ? 6 : 16 );
 
 	/* Calculate pseudo header */
-	memcpy ( pshdr, &iphdr->src, sizeof ( in_addr ) );
-	offset += sizeof ( in_addr );
-	memcpy ( pshdr + offset, &iphdr->dest, sizeof ( in_addr ) );
-	offset += sizeof ( in_addr );
-	*( ( uint8_t* ) ( pshdr + offset++ ) ) = 0x00;
-	*( ( uint8_t* ) ( pshdr + offset++ ) ) = iphdr->protocol;
-	*( ( uint16_t* ) ( pshdr + offset ) ) = pkb_len ( pkb ) - IP_HLEN;
+	pshdr.src = iphdr->src;
+	pshdr.dest = iphdr->dest;
+	pshdr.zero_padding = 0x00;
+	pshdr.protocol = iphdr->protocol;
+	pshdr.len = htons ( pkb_len ( pkb ) - sizeof ( *iphdr ) );
 
 	/* Update the checksum value */
-	*( ( uint16_t* ) csum_offset ) = *( ( uint16_t* ) csum_offset ) + calc_chksum ( pshdr, IP_PSHLEN );
+	*( ( uint16_t* ) csum_offset ) = *( ( uint16_t* ) csum_offset ) + calc_chksum ( &pshdr, IP_PSHLEN );
 }
 
 /**