bug in IP broadcast packet recognition

[bill at cu-arpa]

From: bill at cu-arpa (William A. Nesheim)

Subject: IP sometimes doesn't recognize broadcast packets 
Index:	sys/netinet/ip_input.c 4.2BSD

Description:
	ip_input does not recognize broadcast IP datagrams for addresses
	other than the first interface on a machine.  This breaks rwho,
	and any other programs which depend on UDP broadcasts.

Repeat-By:
	get a machine with 2 or more ethernet (or other broadcast) net
	interfaces, and run rwhod on it.  You will only see information
	from the 1st ethernet on the system, NOT from the second.

Fix:
	In ip_input(), a "quick test" for an address match of the
	incoming packet and the first interface is done, testing
	for both the full address, and the broadcast address, if the
	interface is marked as a broadcast interface.  This works
	for packets with the address of the FIRST interface as their
	destination, but if the dest. is the broadcast address of 
	any other interface, the test in if_ifwithaddr() fails, and
	the packet is handed to ip_forward(), which drops it.

	I replaced the test of the "first" interface with a quick
	trip through ALL the interfaces, and eliminated the call to
	if_ifwithaddr(), as its return value was never used anyway.

	A diff of sys/netinet/ip_input.c follows.
	The line numbers are undoubtedly not what you expect.


RCS file: RCS/ip_input.c,v
retrieving revision 1.4
diff -c -r1.4 ip_input.c
*** /tmp/,RCSt1000175	Mon Dec 17 13:18:09 1984
--- ip_input.c	Mon Dec 17 13:11:49 1984
***************
*** 1,4
! /* $Header: ip_input.c,v 1.4 84/10/12 12:08:33 bill Exp $ */
  /*	ip_input.c	6.3	84/05/25	*/
  
  #include "../h/param.h"

--- 1,4 -----
! /* $Header: ip_input.c,v 1.5 84/12/17 13:10:41 bill Exp $ */
  /*	ip_input.c	6.3	84/05/25	*/
  
  #include "../h/param.h"
***************
*** 146,153
  		goto next;
  
  	/*
! 	 * Fast check on the first internet
! 	 * interface in the list.
  	 */
  	if (ifinet) {
  		struct sockaddr_in *sin;

--- 146,152 -----
  		goto next;
  
  	/*
! 	 *  check for our address
  	 */
  	{
  	register struct sockaddr_in *sin;
***************
*** 149,156
  	 * Fast check on the first internet
  	 * interface in the list.
  	 */
! 	if (ifinet) {
! 		struct sockaddr_in *sin;
  
  		sin = (struct sockaddr_in *)&ifinet->if_addr;
  		if (sin->sin_addr.s_addr == ip->ip_dst.s_addr)

--- 148,156 -----
  	/*
  	 *  check for our address
  	 */
! 	{
! 	register struct sockaddr_in *sin;
! 	register struct ifnet *ifp;
  
  	for(ifp = ifnet; ifp; ifp = ifp->if_next) {
  		if (ifp->if_addr.sa_family != AF_INET)
***************
*** 152,158
  	if (ifinet) {
  		struct sockaddr_in *sin;
  
! 		sin = (struct sockaddr_in *)&ifinet->if_addr;
  		if (sin->sin_addr.s_addr == ip->ip_dst.s_addr)
  			goto ours;
  		sin = (struct sockaddr_in *)&ifinet->if_broadaddr;

--- 152,161 -----
  	register struct sockaddr_in *sin;
  	register struct ifnet *ifp;
  
! 	for(ifp = ifnet; ifp; ifp = ifp->if_next) {
! 		if (ifp->if_addr.sa_family != AF_INET)
! 			continue;
! 		sin = (struct sockaddr_in *)&ifp->if_addr;
  		if (sin->sin_addr.s_addr == ip->ip_dst.s_addr)
  			goto ours;
  		sin = (struct sockaddr_in *)&ifp->if_broadaddr;
***************
*** 155,162
  		sin = (struct sockaddr_in *)&ifinet->if_addr;
  		if (sin->sin_addr.s_addr == ip->ip_dst.s_addr)
  			goto ours;
! 		sin = (struct sockaddr_in *)&ifinet->if_broadaddr;
! 		if ((ifinet->if_flags & IFF_BROADCAST) &&
  		    sin->sin_addr.s_addr == ip->ip_dst.s_addr)
  			goto ours;
  	}

--- 158,165 -----
  		sin = (struct sockaddr_in *)&ifp->if_addr;
  		if (sin->sin_addr.s_addr == ip->ip_dst.s_addr)
  			goto ours;
! 		sin = (struct sockaddr_in *)&ifp->if_broadaddr;
! 		if ((ifp->if_flags & IFF_BROADCAST) &&
  		    sin->sin_addr.s_addr == ip->ip_dst.s_addr)
  			goto ours;
  	}
***************
*** 160,165
  		    sin->sin_addr.s_addr == ip->ip_dst.s_addr)
  			goto ours;
  	}
  /* BEGIN GROT */
  #include "nd.h"
  #if NND > 0

--- 163,170 -----
  		    sin->sin_addr.s_addr == ip->ip_dst.s_addr)
  			goto ours;
  	}
+ 	/* not for us at this point */
+ 	}
  /* BEGIN GROT */
  #include "nd.h"
  #if NND > 0
***************
*** 174,184
  		goto ours;
  #endif
  /* END GROT */
! 	ipaddr.sin_addr = ip->ip_dst;
! 	if (if_ifwithaddr((struct sockaddr *)&ipaddr) == 0) {
! 		ip_forward(ip);
! 		goto next;
! 	}
  
  ours:
  	/*

--- 179,187 -----
  		goto ours;
  #endif
  /* END GROT */
! 
! 	ip_forward(ip);
! 	goto next;
  
  ours:
  	/*