[Qemu-devel] [PATCH] Fix udp slirp to always set from address and port

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

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Attached is a patch to always set the from address and port when using 
slirp "-net user" type networking.  It fixes the case so that the target 
can boot from udp NFS as well as the case where different instances of 
an application over time go through the same redirection port with 
different source ports or addresses.

A possible approach for the future if advanced use cases are required is 
to allow specification of 3 different categories of redirection access.
1) Dynamic port and address (the default with this patch)
2) Dynamic port with static address
3) Dynamic address with static port
4) static port and address

The last 3 would mainly be for security type options if you wanted to 
restrict things.  Items 2-4 can go into a ToDo list somewhere.

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

Jason.

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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;