Re: [Qemu-devel] Re: weird slirp problems (dns lookups stopped working, and maybe more) [PATCH]

[Jason Wessel <jason.wessel@windriver.com>]

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I posted a similar patch last year, but it was not accepted for some 
reason.  Making this change allows UDP nfs to work to a remote file 
server as well.

I would recommend, making one further change as included in this patch.  
It allows KGDBOE to operate on the local host or from a remote host 
because it allow the special 10.0.2.2 address to be translated.

I have included the patch in the e-mail once again.

signed-off-by: jason.wessel@windriver.com

Jason.




Juergen Lock wrote:
> On Wed, Jan 10, 2007 at 12:04:03AM +0100, Juergen Lock wrote:
>   
>> ...
>> Ok, garrison on irc just helped solve this mystery:  This (the same)
>> one actually goes out first, before the 10.0.2.3 one (I didn't notice
>> at first), and since slirp reuses the socket because the source ip and
>> port hasnt changed (slirp/udp.c lines 172 and up, it doesn't check the
>> dest ip), the second packet with the 10.0.2.3 dest ip (which gets
>> replaced with the hosts's dns) goes out wrong.  And the reason this
>> worked previously with the same guest is multicast started working
>> only recently...
>>     
>
> And here's the fix I just added to the FreeBSD qemu port: (thanx garrison!)
>
> Index: qemu/slirp/udp.c
> @@ -205,8 +208,6 @@
>  	  /* udp_last_so = so; */
>  	  so->so_laddr = ip->ip_src;
>  	  so->so_lport = uh->uh_sport;
> -	  so->so_faddr = ip->ip_dst; /* XXX */
> -	  so->so_fport = uh->uh_dport; /* XXX */
>  	  
>  	  if ((so->so_iptos = udp_tos(so)) == 0)
>  	    so->so_iptos = ip->ip_tos;
> @@ -216,6 +217,15 @@
>  	   * and if it is, do the fork_exec() etc.
>  	   */
>  	}
> +
> +	/*
> +	 * Assign destination unconditionally
> +	 *
> +	 * This fixes the case where packets are sent from the same
> +	 * source ip/port to different destination ips/ports
> +	 */
> +	so->so_faddr = ip->ip_dst; /* XXX */
> +	so->so_fport = uh->uh_dport; /* XXX */
>  
>  	iphlen += sizeof(struct udphdr);
>  	m->m_len -= iphlen;
>
>
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>   


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Index: qemu/slirp/udp.c
===================================================================
--- qemu.orig/slirp/udp.c
+++ qemu/slirp/udp.c
@@ -205,8 +205,6 @@ udp_input(m, iphlen)
 	  /* udp_last_so = so; */
 	  so->so_laddr = ip->ip_src;
 	  so->so_lport = uh->uh_sport;
-	  so->so_faddr = ip->ip_dst; /* XXX */
-	  so->so_fport = uh->uh_dport; /* XXX */
 	  
 	  if ((so->so_iptos = udp_tos(so)) == 0)
 	    so->so_iptos = ip->ip_tos;
@@ -216,6 +214,13 @@ udp_input(m, iphlen)
 	   * and if it is, do the fork_exec() etc.
 	   */
 	}
+	/* Always reset the from address as it can change,
+	 * as with NFS for example where it will talk to
+	 * the same destination port with multiple source
+	 * addresses. Or different gdb session to kgdboe.
+	 */
+	so->so_faddr = ip->ip_dst; /* XXX */
+	so->so_fport = uh->uh_dport; /* XXX */
 
 	iphlen += sizeof(struct udphdr);
 	m->m_len -= iphlen;
@@ -312,7 +317,8 @@ int udp_output(struct socket *so, struct
     struct sockaddr_in saddr, daddr;
 
     saddr = *addr;
-    if ((so->so_faddr.s_addr & htonl(0xffffff00)) == special_addr.s_addr) {
+    if ((so->so_faddr.s_addr & htonl(0xffffff00)) == special_addr.s_addr &&
+        addr->sin_addr.s_addr == htonl(0x7f000001)) {
         saddr.sin_addr.s_addr = so->so_faddr.s_addr;
         if ((so->so_faddr.s_addr & htonl(0x000000ff)) == htonl(0xff))
             saddr.sin_addr.s_addr = alias_addr.s_addr;