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

[Jason Wessel]

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: address@hidden

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;
>
>
> _______________________________________________
> Qemu-devel mailing list
> address@hidden
> http://lists.nongnu.org/mailman/listinfo/qemu-devel
>   

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;