Patch by Gleb Paharenko <gpaharenko@gmail.com> for dsniff >= 2.4b1, which
adds checksum for libnids. For further information, please have a look to
Debian bug ID #420129.

--- dsniff-2.4b1/dsniff.c		2007-08-11 01:37:33.000000000 -0300
+++ dsniff-2.4b1/dsniff.c.checksum	2007-08-11 01:38:55.000000000 -0300
@@ -70,6 +70,80 @@
 {
 }
 
+
+static int get_all_ifaces(struct ifreq **, int *);
+static unsigned int get_addr_from_ifreq(struct ifreq *);
+
+int all_local_ipaddrs_chksum_disable()
+{
+	struct ifreq *ifaces;
+	int ifaces_count;
+	int i, ind = 0;
+	struct nids_chksum_ctl *ctlp;
+	unsigned int tmp;
+
+	if (!get_all_ifaces(&ifaces, &ifaces_count))
+		return -1;
+	ctlp =
+	    (struct nids_chksum_ctl *) malloc(ifaces_count *
+					      sizeof(struct
+						     nids_chksum_ctl));
+	if (!ctlp)
+		return -1;
+	for (i = 0; i < ifaces_count; i++) {
+		tmp = get_addr_from_ifreq(ifaces + i);
+		if (tmp) {
+			ctlp[ind].netaddr = tmp;
+			ctlp[ind].mask = inet_addr("255.255.255.255");
+			ctlp[ind].action = NIDS_DONT_CHKSUM;
+			ind++;
+		}
+	}
+	free(ifaces);
+	nids_register_chksum_ctl(ctlp, ind);
+}
+
+/* helper functions for Example 2 */
+unsigned int get_addr_from_ifreq(struct ifreq *iface)
+{
+	if (iface->ifr_addr.sa_family == AF_INET)
+		return ((struct sockaddr_in *) &(iface->ifr_addr))->
+		    sin_addr.s_addr;
+	return 0;
+}
+
+static int get_all_ifaces(struct ifreq **ifaces, int *count)
+{
+	int ifaces_size = 8 * sizeof(struct ifreq);
+	struct ifconf param;
+	int sock;
+	unsigned int i;
+
+	*ifaces = malloc(ifaces_size);
+	sock = socket(PF_INET, SOCK_DGRAM, IPPROTO_IP);
+	if (sock <= 0)
+		return 0;
+	for (;;) {
+		param.ifc_len = ifaces_size;
+		param.ifc_req = *ifaces;
+		if (ioctl(sock, SIOCGIFCONF, &param))
+			goto err;
+		if (param.ifc_len < ifaces_size)
+			break;
+		free(*ifaces);
+		ifaces_size *= 2;
+		ifaces = malloc(ifaces_size);
+	}
+	*count = param.ifc_len / sizeof(struct ifreq);
+	close(sock);
+	return 1;
+      err:
+	close(sock);
+	return 0;
+}
+
+
+
 int
 main(int argc, char *argv[])
 {
@@ -189,6 +263,8 @@
 			warnx("using %s", nids_params.filename);
 		}
 	}
+
+	all_local_ipaddrs_chksum_disable();
 	
 	nids_run();
 	
