Hi Folks, I've been working on fixing some of the kernel level network counters which are used by SNMP, and need a little advice. This is in the 2.4.2 kernel, but appears to be the same in 2.4.7. One of bugs is related to IpInDelivers which is not incremented when an incoming ICMP is delivered to icmp_rcv(). Looked like an easy enough fix by calling IP_INC_STATS_BH(IpInDelivers) at the top of icmp_rcv(). Testing looked good, IpInDelivers now reflected the correct number of delivers based on the network traffic sent and the number of IcmpInMsgs. However, if there is a raw listener registered the counter can now be incremented twice. For example if dhcpd is running. If I've followed the code correctly (I'm relatively new to the Linux IP code), raw_v4_input() is called prior to the protocol specific handler (if required). raw_v4_input() calls raw_rcv() which calls raw_rcv_skb() which increments IpInDelivers. After all the raw processing the protocol specific handler icmp_rcv() is called and IpInDiscards is incremented again. I can think of a few possible solutions: 1. Look at the skb in raw_rcv_skb() and if it looks like an ICMP don't increment the IpInDelivers. Sort of nasty, looking at different level. 2. Don't increment IpInDelivers at all in the raw code. 3. Let it increment it twice as it was delivered to two different handlers. Although this then leads to rather odd counters where IpInDelivers is larger than IpInReceives. IpInDelivers is defined as: "The total number of input datagrams successfully delivered to IP user-protocols (including ICMP)." Looking at the skb would ensure that the counters are correct for both raw and icmp delivers, but is ugly So any advice on what the correct thing to do is, or other suggestions greatly appreciated. Anyway help appreciated. Cheers, Mark. ---------- Mark Price IBM Beaverton, OR - mnprice@us.ibm.com - mprice@sequent.com - : send the line "unsubscribe linux-net" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
