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Clean up the checksumming stuff a bit: 

have "ip_checksum()" compute the checksum of the IP header;

	have "ip_checksum_state()" call "ip_checksum()" and then return
	TRUE if the result is 0 and FALSE otherwise;

	have "ip_checksum_shouldbe()" save the current value of the
	checksum field in the header, set that field to 0, call
	"ip_checksum()" to get the checksum, restore the value of the
	checksum field in the header to the saved value, and then return
	what "ip_checksum()" returned;

rather than having duplicated code to compute checksums.

svn path=/trunk/; revision=2206
This commit is contained in:
Guy Harris 2000-08-04 22:43:45 +00:00
parent b20fbb9d9f
commit 1239d0e5d2
1 changed files with 30 additions and 28 deletions
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58
packet-ip.c
View File

@ -1,7 +1,7 @@
/* packet-ip.c
* Routines for IP and miscellaneous IP protocol packet disassembly
*
* $Id: packet-ip.c,v 1.96 2000/08/04 04:54:22 gram Exp $
* $Id: packet-ip.c,v 1.97 2000/08/04 22:43:45 guy Exp $
*
* Ethereal - Network traffic analyzer
* By Gerald Combs <gerald@zing.org>
@ -776,46 +776,48 @@ static const true_false_string flags_set_truth = {
"Not set"
};
static gboolean ip_checksum_state(e_ip *iph)
{
unsigned long Sum;
unsigned char *Ptr, *PtrEnd;
Sum = 0;
PtrEnd = (lo_nibble(iph->ip_v_hl) * 4 + (char *)iph);
for (Ptr = (unsigned char *) iph; Ptr < PtrEnd; Ptr += 2) {
Sum += pntohs(Ptr);
}
Sum = (Sum & 0xFFFF) + (Sum >> 16);
Sum = (Sum & 0xFFFF) + (Sum >> 16);
if (Sum != 0xffff)
return FALSE;
return TRUE;
}
static unsigned short ip_checksum(e_ip *iph)
static guint16 ip_checksum(e_ip *iph)
{
unsigned long Sum;
unsigned char *Ptr, *PtrEnd;
guint16 ipsum;
Sum = 0;
ipsum = iph->ip_sum;
iph->ip_sum = 0;
PtrEnd = (lo_nibble(iph->ip_v_hl) * 4 + (char *)iph);
for (Ptr = (unsigned char *) iph; Ptr < PtrEnd; Ptr += 2) {
Sum += pntohs(Ptr);
}
iph->ip_sum = ipsum;
Sum = (Sum & 0xFFFF) + (Sum >> 16);
Sum = (Sum & 0xFFFF) + (Sum >> 16);
return((unsigned short)~Sum);
return (guint16)~Sum;
}
static gboolean ip_checksum_state(e_ip *iph)
{
guint16 Sum;
Sum = ip_checksum(iph);
if (Sum != 0)
return FALSE;
return TRUE;
}
static guint16 ip_checksum_shouldbe(e_ip *iph)
{
guint16 ipsum;
guint16 Sum;
ipsum = iph->ip_sum;
iph->ip_sum = 0;
Sum = ip_checksum(iph);
iph->ip_sum = ipsum;
return Sum;
}
void
dissect_ip(const u_char *pd, int offset, frame_data *fd, proto_tree *tree) {
@ -904,7 +906,7 @@ dissect_ip(const u_char *pd, int offset, frame_data *fd, proto_tree *tree) {
else {
proto_tree_add_uint_format(ip_tree, hf_ip_checksum, NullTVB, offset + 10, 2, iph.ip_sum,
"Header checksum: 0x%04x (incorrect, should be 0x%04x)", iph.ip_sum,
ip_checksum((e_ip*) &pd[offset]));
ip_checksum_shouldbe((e_ip*) &pd[offset]));
}
proto_tree_add_ipv4(ip_tree, hf_ip_src, NullTVB, offset + 12, 4, iph.ip_src);