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

From: Hannes Frederic Sowa <[email-masked]>
Date: Wed, 30 Jul 2014 15:45:30 +0200

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.

>  }
>  
>  /*
> 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.

Bye,
Hannes