--- linux-2.6.17/drivers/net/pppoe.c.old	2006-10-10 13:47:56.000000000 +0200
+++ linux-2.6.17/drivers/net/pppoe.c	2006-10-10 13:52:02.000000000 +0200
@@ -600,6 +600,9 @@
 		po->chan.hdrlen = (sizeof(struct pppoe_hdr) +
 				   dev->hard_header_len);
 
+		if (po->chan.mtu > dev->mtu - sizeof(struct pppoe_hdr))
+			po->chan.mtu = dev->mtu - sizeof(struct pppoe_hdr);
+
 		po->chan.private = sk;
 		po->chan.ops = &pppoe_chan_ops;
 
