From dafee490858f79e144c5e6cdd84ceb9efa20a3f1 Mon Sep 17 00:00:00 2001 From: Wei Dong Date: Wed, 2 Aug 2006 13:41:21 -0700 Subject: [PATCH] [IPV6]: SNMPv2 "ipv6IfStatsOutFragCreates" counter error When I tested linux kernel 2.6.71.7 about statistics "ipv6IfStatsOutFragCreates", and found that it couldn't increase correctly. The criteria is RFC 2465: ipv6IfStatsOutFragCreates OBJECT-TYPE SYNTAX Counter32 MAX-ACCESS read-only STATUS current DESCRIPTION "The number of output datagram fragments that have been generated as a result of fragmentation at this output interface." ::= { ipv6IfStatsEntry 15 } I think there are two issues in Linux kernel. 1st: RFC2465 specifies the counter is "The number of output datagram fragments...". I think increasing this counter after output a fragment successfully is better. And it should not be increased even though a fragment is created but failed to output. 2nd: If we send a big ICMP/ICMPv6 echo request to a host, and receive ICMP/ICMPv6 echo reply consisted of some fragments. As we know that in Linux kernel first fragmentation occurs in ICMP layer(maybe saying transport layer is better), but this is not the "real" fragmentation,just do some "pre-fragment" -- allocate space for date, and form a frag_list, etc. The "real" fragmentation happens in IP layer -- set offset and MF flag and so on. So I think in "fast path" for ip_fragment/ip6_fragment, if we send a fragment which "pre-fragment" by upper layer we should also increase "ipv6IfStatsOutFragCreates". Signed-off-by: Wei Dong Acked-by: YOSHIFUJI Hideaki Signed-off-by: David S. Miller --- net/ipv4/ip_output.c | 7 ++++--- net/ipv6/ip6_output.c | 8 +++++--- 2 files changed, 9 insertions(+), 6 deletions(-) diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c index 7c9f9a6421..9bf307a297 100644 --- a/net/ipv4/ip_output.c +++ b/net/ipv4/ip_output.c @@ -526,6 +526,8 @@ int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff*)) err = output(skb); + if (!err) + IP_INC_STATS(IPSTATS_MIB_FRAGCREATES); if (err || !frag) break; @@ -649,9 +651,6 @@ slow_path: /* * Put this fragment into the sending queue. */ - - IP_INC_STATS(IPSTATS_MIB_FRAGCREATES); - iph->tot_len = htons(len + hlen); ip_send_check(iph); @@ -659,6 +658,8 @@ slow_path: err = output(skb2); if (err) goto fail; + + IP_INC_STATS(IPSTATS_MIB_FRAGCREATES); } kfree_skb(skb); IP_INC_STATS(IPSTATS_MIB_FRAGOKS); diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c index 70c9234b70..69451af6ab 100644 --- a/net/ipv6/ip6_output.c +++ b/net/ipv6/ip6_output.c @@ -596,6 +596,9 @@ static int ip6_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *)) } err = output(skb); + if(!err) + IP6_INC_STATS(IPSTATS_MIB_FRAGCREATES); + if (err || !frag) break; @@ -707,12 +710,11 @@ slow_path: /* * Put this fragment into the sending queue. */ - - IP6_INC_STATS(IPSTATS_MIB_FRAGCREATES); - err = output(frag); if (err) goto fail; + + IP6_INC_STATS(IPSTATS_MIB_FRAGCREATES); } kfree_skb(skb); IP6_INC_STATS(IPSTATS_MIB_FRAGOKS); -- 2.39.5