December 29, 2012 01:18 · Dec 29, 2012
diff --git a/route_lookup.c b/route_lookup.c
@@ -0,0 +1,71 @@
+#include <stdio.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#include <unistd.h>
+
+
+int main(int argc, char* argv[])
+{
+    int s;
+    /* struct in_addr addr; */
+    struct sockaddr_in dest = { 0 };
+    dest.sin_family = AF_INET;
+    dest.sin_len = sizeof(struct sockaddr_in);
+    dest.sin_port = 80;
+
+    if(argc < 2)
+    {
+        fprintf(stderr, "not enough arguments: must supply destination ip address\n");
+        return 1;
+    }
+
+    if(0 == inet_aton(argv[1], &dest.sin_addr))
+    {
+        fprintf(stderr, "invalid ip address\n");
+        return 2;
+    }
+
+    s = socket(AF_INET, SOCK_DGRAM, 0);
+    if(s)
+    {
+        struct sockaddr_in sin = { 0 };
+        int result;
+        socklen_t socklen = sizeof(struct sockaddr_in);
+
+        sin.sin_family = AF_INET;
+
+
+        result = bind(s, (struct sockaddr*) &sin, sizeof(struct sockaddr_in));
+        if(0 != result)
+        {
+            perror("bind");
+            goto exit;
+        }
+
+        result = connect(s, (struct sockaddr*) &dest, sizeof(struct sockaddr_in));
+        if(0 != result)
+        {
+            perror("connect");
+            goto exit;
+        }
+
+
+        result = getsockname(s, (struct sockaddr*) &sin, &socklen);
+        if(0 == result)
+        {
+            // printf("sin_family=%d, sin_addr.s_addr=%08x, sin_port=%d\n", sin.sin_family, sin.sin_addr.s_addr, sin.sin_port);
+            printf("Source address: %s\n", inet_ntoa(sin.sin_addr));
+        }
+        else
+        {
+            perror("getsockname");
+        }
+
+
+exit:
+        close(s);
+    }
+
+    return 0;
+}