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--- get_addrs.c
+++ get_addrs.c 1994/02/23 12:41:31
@@ -44,11 +44,33 @@
#include <stdio.h>
#include "talk_ctl.h"
+/*
+ * Hah. BSD folks may have thought too simple on this one.
+ * If you are a multihomed host, this program will miserably fail,
+ * as it will use the IP address of "hostname" as the source of the
+ * messages, not the address of the interface over which the packet
+ * will be routed.
+ *
+ * With Linux NET-2E, a possible solution is to perform an UDP CONNECT
+ * operation on a socket, so the kernel sets the correct source address
+ * of the socket's packets. Then we do a getsockname on that socket,
+ * and voila... we have the correct source address!
+ *
+ * Note that this only works with NET-2E BETA-4 and newer kernels.
+ */
get_addrs(my_machine_name, his_machine_name)
char *my_machine_name, *his_machine_name;
{
struct hostent *hp;
struct servent *sp;
+#ifdef __linux__
+ struct sockaddr_in sin;
+ struct sockaddr_in foo;
+ int sock, i;
+
+ /* If socket fails, code will see it. */
+ sock = socket(AF_INET, SOCK_DGRAM, 0);
+#endif
msg.pid = htonl(getpid());
/* look up the address of the local host */
@@ -81,4 +103,22 @@
exit(-1);
}
daemon_port = sp->s_port;
+#ifdef __linux__
+ sin.sin_family = AF_INET;
+ sin.sin_addr.s_addr = his_machine_addr.s_addr;
+ sin.sin_port = sp->s_port;
+
+ /* Now here is the trick. We connect to the other side. */
+ if ((sock >= 0) &&
+ (connect(sock, (struct sockaddr *) &sin, sizeof(sin)) == 0)) {
+ /* Bingo. Now fetch the address. */
+ foo = sin;
+ i = sizeof(foo);
+ if (getsockname(sock, (struct sockaddr *) &foo, &i) == 0) {
+ my_machine_addr = foo.sin_addr;
+ }
+ }
+ /* Loose the socket. */
+ (void) close(sock);
+#endif
}
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