Subject: Re: [PATCH] net: fix the counter ICMP_MIB_INERRORS/ICMP6_MIB_INERRORS

From: Duan Jiong <[email-masked]>
Date: Thu, 31 Jul 2014 10:58:28 +0800

On 07/30/2014 09:45 PM, Hannes Frederic Sowa wrote:
> On Di, 2014-07-29 at 16:19 +0800, Duan Jiong wrote:
>> When dealing with ICMPv[46] Error Message, function icmp_socket_deliver()
>> and icmpv6_notify() do some valid checks on packet's length, but then some
>> protocols check packet's length redaudantly. So remove those duplicated
>> statements, and increase counter ICMP_MIB_INERRORS/ICMP6_MIB_INERRORS in
>> function icmp_socket_deliver() and icmpv6_notify() respectively.
>>
>> In addition, add missed counter in udp6/udplite6 when socket is NULL.
> 
> I am ok with adding the error counters, but...
> 
>> ---
>>  net/ipv4/icmp.c     |  4 +++-
>>  net/ipv4/tcp_ipv4.c |  5 -----
>>  net/ipv6/icmp.c     | 11 ++++++++---
>>  net/ipv6/udp.c      |  8 ++++++--
>>  net/sctp/input.c    |  5 -----
>>  5 files changed, 17 insertions(+), 16 deletions(-)
>>
>> diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
>> index 42b7bcf..092400e 100644
>> --- a/net/ipv4/icmp.c
>> +++ b/net/ipv4/icmp.c
>> @@ -663,8 +663,10 @@ static void icmp_socket_deliver(struct sk_buff *skb, u32 info)
>>  	/* Checkin full IP header plus 8 bytes of protocol to
>>  	 * avoid additional coding at protocol handlers.
>>  	 */
>> -	if (!pskb_may_pull(skb, iph->ihl * 4 + 8))
>> +	if (!pskb_may_pull(skb, iph->ihl * 4 + 8)) {
>> +		ICMP_INC_STATS_BH(dev_net(skb->dev), ICMP_MIB_INERRORS);
>>  		return;
>> +	}
>>  
>>  	raw_icmp_error(skb, protocol, info);
>>  
>> diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
>> index 77cccda..715cf6b 100644
>> --- a/net/ipv4/tcp_ipv4.c
>> +++ b/net/ipv4/tcp_ipv4.c
>> @@ -342,11 +342,6 @@ void tcp_v4_err(struct sk_buff *icmp_skb, u32 info)
>>  	int err;
>>  	struct net *net = dev_net(icmp_skb->dev);
>>  
>> -	if (icmp_skb->len < (iph->ihl << 2) + 8) {
>> -		ICMP_INC_STATS_BH(net, ICMP_MIB_INERRORS);
>> -		return;
>> -	}
>> -
>>  	sk = inet_lookup(net, &tcp_hashinfo, iph->daddr, th->dest,
>>  			iph->saddr, th->source, inet_iif(icmp_skb));
>>  	if (!sk) {
>> diff --git a/net/ipv6/icmp.c b/net/ipv6/icmp.c
>> index f6c84a6..8ca3cc0 100644
>> --- a/net/ipv6/icmp.c
>> +++ b/net/ipv6/icmp.c
>> @@ -626,9 +626,10 @@ void icmpv6_notify(struct sk_buff *skb, u8 type, u8 code, __be32 info)
>>  	int inner_offset;
>>  	__be16 frag_off;
>>  	u8 nexthdr;
>> +	struct net *net = dev_net(skb->dev);
>>  
>>  	if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
>> -		return;
>> +		goto out;
>>  
>>  	nexthdr = ((struct ipv6hdr *)skb->data)->nexthdr;
>>  	if (ipv6_ext_hdr(nexthdr)) {
>> @@ -636,14 +637,14 @@ void icmpv6_notify(struct sk_buff *skb, u8 type, u8 code, __be32 info)
>>  		inner_offset = ipv6_skip_exthdr(skb, sizeof(struct ipv6hdr),
>>  						&nexthdr, &frag_off);
>>  		if (inner_offset<0)
>> -			return;
>> +			goto out;
>>  	} else {
>>  		inner_offset = sizeof(struct ipv6hdr);
>>  	}
>>  
>>  	/* Checkin header including 8 bytes of inner protocol header. */
>>  	if (!pskb_may_pull(skb, inner_offset+8))
>> -		return;
>> +		goto out;
>>  
>>  	/* BUGGG_FUTURE: we should try to parse exthdrs in this packet.
>>  	   Without this we will not able f.e. to make source routed
>> @@ -659,6 +660,10 @@ void icmpv6_notify(struct sk_buff *skb, u8 type, u8 code, __be32 info)
>>  	rcu_read_unlock();
>>  
>>  	raw6_icmp_error(skb, nexthdr, type, code, inner_offset, info);
>> +	return;
>> +
>> +out:
>> +	ICMP6_INC_STATS_BH(net, __in6_dev_get(skb->dev), ICMP6_MIB_INERRORS);
> 
> ... please don't use __in6_dev_get in BH without rcu, but inet6_iif. You
> risk a lockdep error otherwise. You don't have rtnl locked and no RCU
> read lock.
> 

May be we can use in6_dev_get instead of __in6_dev_get, and 
use in6_dev_put to release the reference later.

>>  }
>>  
>>  /*
>> diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
>> index 7092ff7..f13d297 100644
>> --- a/net/ipv6/udp.c
>> +++ b/net/ipv6/udp.c
>> @@ -534,11 +534,15 @@ void __udp6_lib_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
>>  	struct udphdr *uh = (struct udphdr*)(skb->data+offset);
>>  	struct sock *sk;
>>  	int err;
>> +	struct net *net = dev_net(skb->dev);
>>  
>> -	sk = __udp6_lib_lookup(dev_net(skb->dev), daddr, uh->dest,
>> +	sk = __udp6_lib_lookup(net, daddr, uh->dest,
>>  			       saddr, uh->source, inet6_iif(skb), udptable);
>> -	if (sk == NULL)
>> +	if (sk == NULL) {
>> +		ICMP6_INC_STATS_BH(net, __in6_dev_get(skb->dev),
>> +				   ICMP6_MIB_INERRORS);
> 
> It is not really necessary here, as you like.
> 

I add it just because i saw the same statements in dccp6/sctp6/tcp6 error
handler.

Thanks,
  Duan

> Bye,
> Hannes
> .