kvm tools: Implement IP checksum for uip

Other protocal, e.g. TCP, UDP, ICMP, can use uip_csum() to make
checsksum as well.

Signed-off-by: Asias He <asias.hejun@gmail.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>

Makefile

@@ -48,6 +48,7 @@ OBJS	+= irq.o
 OBJS	+= uip/arp.o
 OBJS	+= uip/ipv4.o
 OBJS	+= uip/buf.o
+OBJS	+= uip/csum.o
 OBJS	+= kvm-cmd.o
 OBJS	+= kvm-debug.o
 OBJS	+= kvm-help.o

include/kvm/uip.h

@@ -103,6 +103,8 @@ static inline u16 uip_ip_len(struct uip_ip *ip)
 int uip_tx_do_ipv4(struct uip_tx_arg *arg);
 int uip_tx_do_arp(struct uip_tx_arg *arg);
 
+u16 uip_csum_ip(struct uip_ip *ip);
+
 struct uip_buf *uip_buf_set_used(struct uip_info *info, struct uip_buf *buf);
 struct uip_buf *uip_buf_set_free(struct uip_info *info, struct uip_buf *buf);
 struct uip_buf *uip_buf_get_used(struct uip_info *info);

uip/csum.c

@@ -0,0 +1,25 @@
+#include "kvm/uip.h"
+
+static u16 uip_csum(u16 csum, u8 *addr, u16 count)
+{
+	long sum = csum;
+
+	while (count > 1) {
+		sum	+= *(u16 *)addr;
+		addr	+= 2;
+		count	-= 2;
+	}
+
+	if (count > 0)
+		sum += *(unsigned char *)addr;
+
+	while (sum>>16)
+		sum = (sum & 0xffff) + (sum >> 16);
+
+	return ~sum;
+}
+
+u16 uip_csum_ip(struct uip_ip *ip)
+{
+	return uip_csum(0, &ip->vhl, uip_ip_hdrlen(ip));
+}