From mboxrd@z Thu Jan 1 00:00:00 1970 From: ebiederm@xmission.com (Eric W. Biederman) Subject: FYI: tftp-hpa breaks when used on secondary ip addresses Date: Fri, 04 Mar 2011 16:58:55 -0800 Message-ID: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Joel Sing , David Miller To: "H. Peter Anvin" , Return-path: Received: from out01.mta.xmission.com ([166.70.13.231]:46571 "EHLO out01.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760039Ab1CEA7B (ORCPT ); Fri, 4 Mar 2011 19:59:01 -0500 Sender: netdev-owner@vger.kernel.org List-ID: tftp-hpa has code to test to see if the address it received a connection on is a local address. I don't have a clue why tftp-hpa doesn't trust the kernel but the code looks like: static int address_is_local(const struct sockaddr_in *addr) { struct sokcaddr sa; int sockfd = -1; sockfd = socket(AF_INET, SOCK_DGRAM, 0); connect(sockfd, (struct sockaddr *)&addr, sizeof(*addr)); getsockname(sockfd, (struct sockaddr *)&sa, sizeof(sa)); return sa.sin_addr.s_addr == addr->sin_addr.s_addr; } Which if fails now if you happen to be running tftp-hpa on a secondary ip address on the same subnet as your first ip. Because pref_source in the routing table points at the first ip. The change in kernel behavior appears to be from the commit below to honor the preferred source address in local connections. This all seems very fuzzy to me and mostly this appears to be a bug in tftp-hpa but since I tracked it down I figured I would let everyone know what happened. Eric commit 9fc3bbb4a752f108cf096d96640f3b548bbbce6c Author: Joel Sing Date: Mon Jan 3 20:24:20 2011 +0000 ipv4/route.c: respect prefsrc for local routes The preferred source address is currently ignored for local routes, which results in all local connections having a src address that is the same as the local dst address. Fix this by respecting the preferred source address when it is provided for local routes. This bug can be demonstrated as follows: # ifconfig dummy0 192.168.0.1 # ip route show table local | grep local.*dummy0 local 192.168.0.1 dev dummy0 proto kernel scope host src # 192.168.0.1 # ip route change table local local 192.168.0.1 dev dummy0 \ proto kernel scope host src 127.0.0.1 # ip route show table local | grep local.*dummy0 local 192.168.0.1 dev dummy0 proto kernel scope host src # 127.0.0.1 We now establish a local connection and verify the source IP address selection: # nc -l 192.168.0.1 3128 & # nc 192.168.0.1 3128 & # netstat -ant | grep 192.168.0.1:3128.*EST tcp 0 0 192.168.0.1:3128 192.168.0.1:33228 # ESTABLISHED tcp 0 0 192.168.0.1:33228 192.168.0.1:3128 # ESTABLISHED Signed-off-by: Joel Sing Signed-off-by: David S. Miller diff --git a/net/ipv4/route.c b/net/ipv4/route.c index df948b0..93bfd95 100644 --- a/net/ipv4/route.c +++ b/net/ipv4/route.c @@ -2649,8 +2649,12 @@ static int ip_route_output_slow(struct net *net, struct rtable **rp, } if (res.type == RTN_LOCAL) { - if (!fl.fl4_src) - fl.fl4_src = fl.fl4_dst; + if (!fl.fl4_src) { + if (res.fi->fib_prefsrc) + fl.fl4_src = res.fi->fib_prefsrc; + else + fl.fl4_src = fl.fl4_dst; + } dev_out = net->loopback_dev; fl.oif = dev_out->ifindex; res.fi = NULL;