TCP connect(2) returns 0 if a routing loop causes an ICMP unreach-time-
	exceeded to be returned.  Problem is that the cmd code is mapped to
	error 0 in in_input.

Fix: b:/usr/src/sys/netinet $ diff -u ip_input.c.orig ip_input.c


Here's the test prog:

/*	conntime.c	Barney Wolff	<barney@databus.com>	*/

#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/sockio.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <signal.h>
#include <sys/errno.h>
extern int errno;
#include <sys/time.h>

#ifdef __FreeBSD__
#define sigignore(x) signal(x,SIG_IGN)
#endif

main(int argc,char **argv) {
	int sockfd,lsockfd,i,recv=0,cookie=0,dofork=0;
	struct sockaddr_in skinaddr;
	struct timeval start,end;

	if (argc < 3) {
		fprintf(stderr,"%0 ipaddr port\n");
		exit(1);
	}

	sigignore(SIGPIPE);

	memset(&skinaddr,0,sizeof(skinaddr));
	skinaddr.sin_family = AF_INET;
	skinaddr.sin_addr.s_addr = inet_addr(argv[1]);
	skinaddr.sin_port = htons((short)atoi(argv[2]));

	if ((sockfd=socket(PF_INET,SOCK_STREAM,0)) < 0)
		{perror("socket"); exit(2);}

	i = 1;
	setsockopt(sockfd,SOL_SOCKET,SO_KEEPALIVE,&i,sizeof(i));

	gettimeofday(&start,NULL);
	i = connect(sockfd,(struct sockaddr *)&skinaddr,sizeof(skinaddr));
	gettimeofday(&end,NULL);

	if (i < 0) perror("connection failed");
	fprintf(stderr,"connect returned in %d usec\n",
		1000000*(end.tv_sec-start.tv_sec)+end.tv_usec-start.tv_usec);
	if (i == 0) {
		start = end;
		i = write(sockfd,"GET /\r\n\r\n",9);
		gettimeofday(&end,NULL);
		if (i < 0) perror("write failed");
		fprintf(stderr,"write returned in %d usec\n",
			1000000*(end.tv_sec-start.tv_sec)+end.tv_usec-start.tv_usec);
	}
}--xhbVGMPOMUOgAjfUvNekJ1eCoXTRrrX5n9EaPLwAq2SxdYNr
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--- ip_input.c.orig     Wed Apr  9 14:07:16 2003
+++ ip_input.c  Fri Apr 11 17:54:11 2003
@@ -1696,7 +1696,7 @@
        0,              EMSGSIZE,       EHOSTDOWN,      EHOSTUNREACH,
        EHOSTUNREACH,   EHOSTUNREACH,   ECONNREFUSED,   ECONNREFUSED,
        EMSGSIZE,       EHOSTUNREACH,   0,              0,
-       0,              0,              0,              0,
+       0,              0,              EHOSTUNREACH,   0,
        ENOPROTOOPT,    ECONNREFUSED
 };
  
(This patch is to current.)
How-To-Repeat: 	Set up routing loop (I just added a /32 bogus route on my internal net
	to do this).  Connect to looped destination.  Connect returns 0, but
	socket is of course not writable.  Test prog attached.  This fails on
	both stable and current.