1 files changed, 258 insertions, 0 deletions
diff --git a/nicutils.c b/nicutils.c
new file mode 100644
index 0000000..4396858
--- /dev/null
+++ b/nicutils.c
@@ -0,0 +1,258 @@
+/*
+ * nicutils.c
+ *
+ *  Created on: 16 Aug 2012
+ *      Author: daniel
+ */
+
+#include "nicutils.h"
+
+#include <stdbool.h>
+#include <string.h>
+#include <stdlib.h>
+#include <sys/socket.h>
+#include <arpa/inet.h>
+#include <net/if.h>
+#include <netinet/if_ether.h>
+#include <netdb.h>
+#include <netinet/in.h>
+#include <linux/netlink.h>
+#include <linux/rtnetlink.h>
+#include <netinet/ether.h>
+#include <stdio.h>
+#include <sys/ioctl.h>
+#include <sys/types.h>
+#include <string.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#define BUFSIZE 8192
+
+static int netlink_createsock()
+{
+	return socket(PF_NETLINK, SOCK_DGRAM, NETLINK_ROUTE);
+}
+
+static int netlink_sendmessage(int sock, struct nlmsghdr* msg)
+{
+	return send(sock, msg, msg->nlmsg_len, 0);
+}
+
+static int netlink_readsock(int sockFd, char *bufPtr, int seqNum, int pId, int buffsize)
+{
+
+	struct nlmsghdr *nlHdr;
+	int readLen = 0, msgLen = 0;
+
+	do {
+		/* Receive response from the kernel */
+		if ((readLen = recv(sockFd, bufPtr, buffsize - msgLen, 0)) < 0) {
+			return -1;
+		}
+
+		nlHdr = (struct nlmsghdr *) bufPtr;
+
+		/* Check if the header is valid */
+		if ((NLMSG_OK(nlHdr, readLen) == 0) || (nlHdr->nlmsg_type == NLMSG_ERROR)) {
+			return -1;
+		}
+
+		/* Check if the its the last message */
+		if (nlHdr->nlmsg_type == NLMSG_DONE) {
+			break;
+		}
+
+		else {
+			/* Else move the pointer to buffer appropriately */
+			bufPtr += readLen;
+			msgLen += readLen;
+		}
+
+		/* Check if its a multi part message */
+		if ((nlHdr->nlmsg_flags & NLM_F_MULTI) == 0) {
+			break;
+		}
+	} while ((nlHdr->nlmsg_seq != seqNum) || (nlHdr->nlmsg_pid != pId));
+
+	return msgLen;
+}
+
+static bool route_finddefault(struct nlmsghdr *nlHdr, char* ifname)
+{
+
+	// unwrap the data
+	struct rtmsg* rtMsg = (struct rtmsg *) NLMSG_DATA(nlHdr);
+
+	/* If the route is not for AF_INET or does not belong to main routing table
+	 then return. */
+	if ((rtMsg->rtm_family != AF_INET) || (rtMsg->rtm_table != RT_TABLE_MAIN)) {
+		return NULL;
+	}
+
+	/* get the rtattr field */
+	struct rtattr* rtAttr = (struct rtattr *) RTM_RTA(rtMsg);
+
+	int rtLen = RTM_PAYLOAD(nlHdr);
+
+	// the idea here is that this doesn't get touched if the
+	// dst is 0 as the response doesn't contain an RTA_DST attribute
+	u_int dst = 0;
+
+	// bash through the attributes
+	for (; RTA_OK(rtAttr, rtLen); rtAttr = RTA_NEXT(rtAttr, rtLen)) {
+		switch (rtAttr->rta_type) {
+		case RTA_OIF:
+			if_indextoname(*(int *) RTA_DATA(rtAttr), ifname);
+			break;
+		case RTA_DST:
+			dst = *((u_int*) RTA_DATA(rtAttr));
+			break;
+		}
+		// We already know we don't want this route, so get out of here
+		if (dst != 0) {
+			break;
+		}
+	}
+
+	return dst == 0;
+}
+
+static char* route_defaultrouteint()
+{
+
+	int sock, len, msgSeq = 0;
+
+	/* Create Socket */
+	if ((sock = netlink_createsock()) < 0) {
+		goto exit;
+	}
+
+	/* Initialize the buffer */
+	char* msgBuf = calloc(BUFSIZE, 1);
+	if (msgBuf == NULL) {
+		goto exit;
+	}
+
+	/* point the header and the msg structure pointers into the buffer */
+	struct nlmsghdr* nlMsg = (struct nlmsghdr *) msgBuf;
+	struct rtmsg* rtMsg = (struct rtmsg *) NLMSG_DATA(nlMsg);
+
+	/* Fill in the nlmsg header*/
+	nlMsg->nlmsg_len = NLMSG_LENGTH(sizeof(struct rtmsg)); // Length of message.
+	nlMsg->nlmsg_type = RTM_GETROUTE; // Get the routes from kernel routing table .
+	nlMsg->nlmsg_flags = NLM_F_DUMP | NLM_F_REQUEST; // The message is a request for dump.
+	nlMsg->nlmsg_seq = msgSeq++; // Sequence of the message packet.
+	nlMsg->nlmsg_pid = getpid(); // PID of process sending the request.
+
+	/* Send the request */
+	if (netlink_sendmessage(sock, nlMsg) < 0) {
+		goto exit;
+	}
+
+	/* Read the response */
+	if ((len = netlink_readsock(sock, msgBuf, msgSeq, getpid(), BUFSIZE)) < 0) {
+		goto exit;
+	}
+
+	static char ifname[256];
+	for (; NLMSG_OK(nlMsg,len); nlMsg = NLMSG_NEXT(nlMsg,len)) {
+		if (route_finddefault(nlMsg, ifname)) {
+			break;
+		}
+	}
+
+exit:
+
+	if (sock >= 0) {
+		close(sock);
+	}
+
+	if (msgBuf != NULL) {
+		free(msgBuf);
+	}
+
+	return ifname;
+}
+
+static bool nicutils_info(char* intefacename, nicinfo* result)
+{
+
+	bool ret = false;
+
+	// get a socket to do the ioctl requests with
+	int sock = socket(PF_INET, SOCK_DGRAM, 0);
+	if (sock < 0) {
+		goto exit;
+	}
+
+	// setup an ifconf struct, allocate a buffer for the data and get
+	// all of the interfaces attached to the system that are up
+	struct ifconf interfaces;
+	interfaces.ifc_len = sizeof(struct ifreq) * 32; // enough space for 32 interfaces.. more than enough
+	interfaces.ifc_buf = malloc(interfaces.ifc_len);
+	if (ioctl(sock, SIOCGIFCONF, &interfaces) < 0) {
+		goto exit;
+	}
+
+	struct ifreq *ifr = interfaces.ifc_req;
+	int i;
+	for (i = 0; i < interfaces.ifc_len / sizeof(struct ifreq); i++) {
+		// is this the interface we want?
+		if (strcmp(ifr[i].ifr_name, intefacename) != 0) {
+			continue;        // skip over this one
+		}
+
+		// get the address
+		struct sockaddr* addr = &(ifr[i].ifr_addr);
+
+		// handle ipv4 and ipv6 addresses..
+		switch (addr->sa_family) {
+		case AF_INET:
+			inet_ntop(AF_INET, &(((struct sockaddr_in *) addr)->sin_addr), result->ip, INET6_ADDRSTRLEN);
+			break;
+
+		case AF_INET6:
+			inet_ntop(AF_INET6, &(((struct sockaddr_in6 *) addr)->sin6_addr), result->ip, INET6_ADDRSTRLEN);
+			break;
+
+		default:
+			snprintf(result->ip, sizeof(result->ip), "shouldneverhappen");
+			break;
+		}
+
+		// get the mac address
+		if (ioctl(sock, SIOCGIFHWADDR, &ifr[i]) < 0) {
+			goto exit;
+		}
+
+		// turn it into a nice string
+		snprintf(result->mac, sizeof(result->mac), "%02x:%02x:%02x:%02x:%02x:%02x",
+		         (unsigned char) ifr[i].ifr_hwaddr.sa_data[0],
+		         (unsigned char) ifr[i].ifr_hwaddr.sa_data[1],
+		         (unsigned char) ifr[i].ifr_hwaddr.sa_data[2],
+		         (unsigned char) ifr[i].ifr_hwaddr.sa_data[3],
+		         (unsigned char) ifr[i].ifr_hwaddr.sa_data[4],
+		         (unsigned char) ifr[i].ifr_hwaddr.sa_data[5]);
+
+		ret = true;
+		break; // break out of the loop
+	}
+
+exit:
+	if (interfaces.ifc_buf != NULL) {
+		free(interfaces.ifc_buf);
+	}
+
+	return ret;
+}
+
+bool nicutils_infofordefaultroute(nicinfo* result)
+{
+
+	char* defaultroute = route_defaultrouteint();
+	if (defaultroute == NULL) {
+		return false;
+	}
+
+	return nicutils_info(defaultroute, result);
+}