ARP bug and a patch

From: zhongyu (xxx_pku@yahoo.com)
Date: Sat Nov 17 2001 - 06:37:50 EST


        Bug's description :
        A computer has two ethernet cards connected to the same hub, each ethernet card was in a
different logical sub net and turn on the ip_forward on each ethernet card. Dozens of ARP request
packet will cause a "neibour table overflow"
error then the netcard can not work .
        reason:
        The arp_rcv fuction would call the ip_route_input function to build the dst entry of the skb.
When the ip_forward is on , the code will run direct into the rt_intern_hash fuction which add the
target ip to the neighbour buffer .
        patch:

diff -Naur linux-2.4.9/net/ipv4/route.c linux-2.4.9n/net/ipv4/route.c
--- linux-2.4.9/net/ipv4/route.c Fri Nov 16 17:19:06 2001
+++ linux-2.4.9n/net/ipv4/route.c Fri Nov 16 17:17:59 2001
@@ -1501,6 +1501,12 @@
        }
 #endif

+ if (skb->protocol == __constant_htons(ETH_P_ARP)){
+ skb->dst = rth;
+ err = 0;
+ goto done;
+ }
+
 intern:
        err = rt_intern_hash(hash, rth, (struct rtable**)&skb->dst);
 done:

          zhongyu
            xxx_pku@yahoo.com

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This archive was generated by hypermail 2b29 : Fri Nov 23 2001 - 21:00:15 EST