Subject: Re: [patch (for 2.6.25?) 1/2] The kernel gets no IP from some DHCP servers

From: Stephen Hemminger <[email-masked]>
Date: Tue, 4 Mar 2008 16:23:42 -0800

On Tue, 04 Mar 2008 14:56:48 -0800
[email-masked] wrote:

> From: "Wappler Marcel" <[email-masked]>
> 
> This patch fixes a DHCP issue of the kernel: some DHCP servers (i.e.  in the
> Linksys WRT54Gv5) are very strict about the contents of the DHCPDISCOVER
> packet they receive from clients.
> 
> Table 5 in RFC2131 page 36 requests the fields 'ciaddr' and 'siaddr' MUST be
> set to '0'.  These DHCP servers ignore Linux kernel's DHCP discovery packets
> with these two fields set to '255.255.255.255' (in contrast to popular DHCP
> clients, such as 'dhclient' or 'udhcpc').  This leads to a not booting system.
> 
> I tested this on a ARM embedded device mounting rootfs over NFS obtaining its
> IP from a Linksys WRT54Gv5 Router running VxWorks and a PC based Server
> running a Linux.  Changing the two fields to '0.0.0.0' worked.
> 
> Cc: Stephen Hemminger <[email-masked]>
> Cc: "David S. Miller" <[email-masked]>
> Cc: Patrick McHardy <[email-masked]>
> Signed-off-by: Andrew Morton <[email-masked]>
> ---

Same patch without the noise comment and extra code.

--- a/net/ipv4/ipconfig.c	2008-03-04 16:20:10.000000000 -0800
+++ b/net/ipv4/ipconfig.c	2008-03-04 16:22:49.000000000 -0800
@@ -753,9 +753,9 @@ static void __init ic_bootp_send_if(stru
 		printk("Unknown ARP type 0x%04x for device %s\n", dev->type, dev->name);
 		b->htype = dev->type; /* can cause undefined behavior */
 	}
+
+	/* server_ip and your_ip address are both already zero per RFC2131 */
 	b->hlen = dev->addr_len;
-	b->your_ip = NONE;
-	b->server_ip = NONE;
 	memcpy(b->hw_addr, dev->dev_addr, dev->addr_len);
 	b->secs = htons(jiffies_diff / HZ);
 	b->xid = d->xid;