Subject: Re: [patch net-next 2/2] netfilter: push reasm skb through instead of original frag skbs

From: Marcelo Ricardo Leitner <[email-masked]>
Date: Thu, 07 Nov 2013 10:52:00 -0200

Em 06-11-2013 14:52, Jiri Pirko escreveu:
> Pushing original fragments through causes several problems. For example
> for matching, frags may not be matched correctly. Take following
> example:
>
> <example>
> On HOSTA do:
> ip6tables -I INPUT -p icmpv6 -j DROP
> ip6tables -I INPUT -p icmpv6 -m icmp6 --icmpv6-type 128 -j ACCEPT
>
> and on HOSTB you do:
> ping6 HOSTA -s2000    (MTU is 1500)
>
> Incoming echo requests will be filtered out on HOSTA. This issue does
> not occur with smaller packets than MTU (where fragmentation does not happen)
> </example>
>
> As was discussed previously, the only correct solution seems to be to use
> reassembled skb instead of separete frags. Doing this has positive side
          just a typo here   ------^

> effects in reducing sk_buff by one pointer (nfct_reasm) and also the reams
                                                          and here   ------^

> dances in ipvs and conntrack can be removed.
>
> Future plan is to remove net/ipv6/netfilter/nf_conntrack_reasm.c
> entirely and use code in net/ipv6/reassembly.c instead.
>
> Signed-off-by: Jiri Pirko <[email-masked]>

Signed-off-by: Marcelo Ricardo Leitner <[email-masked]>

> ---
>   include/linux/skbuff.h                         | 32 ---------------
>   include/net/ip_vs.h                            | 32 +--------------
>   include/net/netfilter/ipv6/nf_defrag_ipv6.h    |  4 +-
>   net/core/skbuff.c                              |  3 --
>   net/ipv6/netfilter/nf_conntrack_l3proto_ipv6.c | 56 +-------------------------
>   net/ipv6/netfilter/nf_conntrack_reasm.c        | 19 +--------
>   net/ipv6/netfilter/nf_defrag_ipv6_hooks.c      |  7 +++-
>   net/netfilter/ipvs/ip_vs_core.c                | 55 +------------------------
>   net/netfilter/ipvs/ip_vs_pe_sip.c              |  8 +---
>   9 files changed, 13 insertions(+), 203 deletions(-)
>
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index 2e153b6..8351614 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -337,11 +337,6 @@ typedef unsigned int sk_buff_data_t;
>   typedef unsigned char *sk_buff_data_t;
>   #endif
>
> -#if defined(CONFIG_NF_DEFRAG_IPV4) || defined(CONFIG_NF_DEFRAG_IPV4_MODULE) || \
> -    defined(CONFIG_NF_DEFRAG_IPV6) || defined(CONFIG_NF_DEFRAG_IPV6_MODULE)
> -#define NET_SKBUFF_NF_DEFRAG_NEEDED 1
> -#endif
> -
>   /**
>    *	struct sk_buff - socket buffer
>    *	@next: Next buffer in list
> @@ -374,7 +369,6 @@ typedef unsigned char *sk_buff_data_t;
>    *	@protocol: Packet protocol from driver
>    *	@destructor: Destruct function
>    *	@nfct: Associated connection, if any
> - *	@nfct_reasm: netfilter conntrack re-assembly pointer
>    *	@nf_bridge: Saved data about a bridged frame - see br_netfilter.c
>    *	@skb_iif: ifindex of device we arrived on
>    *	@tc_index: Traffic control index
> @@ -463,9 +457,6 @@ struct sk_buff {
>   #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
>   	struct nf_conntrack	*nfct;
>   #endif
> -#ifdef NET_SKBUFF_NF_DEFRAG_NEEDED
> -	struct sk_buff		*nfct_reasm;
> -#endif
>   #ifdef CONFIG_BRIDGE_NETFILTER
>   	struct nf_bridge_info	*nf_bridge;
>   #endif
> @@ -2594,18 +2585,6 @@ static inline void nf_conntrack_get(struct nf_conntrack *nfct)
>   		atomic_inc(&nfct->use);
>   }
>   #endif
> -#ifdef NET_SKBUFF_NF_DEFRAG_NEEDED
> -static inline void nf_conntrack_get_reasm(struct sk_buff *skb)
> -{
> -	if (skb)
> -		atomic_inc(&skb->users);
> -}
> -static inline void nf_conntrack_put_reasm(struct sk_buff *skb)
> -{
> -	if (skb)
> -		kfree_skb(skb);
> -}
> -#endif
>   #ifdef CONFIG_BRIDGE_NETFILTER
>   static inline void nf_bridge_put(struct nf_bridge_info *nf_bridge)
>   {
> @@ -2624,10 +2603,6 @@ static inline void nf_reset(struct sk_buff *skb)
>   	nf_conntrack_put(skb->nfct);
>   	skb->nfct = NULL;
>   #endif
> -#ifdef NET_SKBUFF_NF_DEFRAG_NEEDED
> -	nf_conntrack_put_reasm(skb->nfct_reasm);
> -	skb->nfct_reasm = NULL;
> -#endif
>   #ifdef CONFIG_BRIDGE_NETFILTER
>   	nf_bridge_put(skb->nf_bridge);
>   	skb->nf_bridge = NULL;
> @@ -2649,10 +2624,6 @@ static inline void __nf_copy(struct sk_buff *dst, const struct sk_buff *src)
>   	nf_conntrack_get(src->nfct);
>   	dst->nfctinfo = src->nfctinfo;
>   #endif
> -#ifdef NET_SKBUFF_NF_DEFRAG_NEEDED
> -	dst->nfct_reasm = src->nfct_reasm;
> -	nf_conntrack_get_reasm(src->nfct_reasm);
> -#endif
>   #ifdef CONFIG_BRIDGE_NETFILTER
>   	dst->nf_bridge  = src->nf_bridge;
>   	nf_bridge_get(src->nf_bridge);
> @@ -2664,9 +2635,6 @@ static inline void nf_copy(struct sk_buff *dst, const struct sk_buff *src)
>   #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
>   	nf_conntrack_put(dst->nfct);
>   #endif
> -#ifdef NET_SKBUFF_NF_DEFRAG_NEEDED
> -	nf_conntrack_put_reasm(dst->nfct_reasm);
> -#endif
>   #ifdef CONFIG_BRIDGE_NETFILTER
>   	nf_bridge_put(dst->nf_bridge);
>   #endif
> diff --git a/include/net/ip_vs.h b/include/net/ip_vs.h
> index cd7275f..5679d92 100644
> --- a/include/net/ip_vs.h
> +++ b/include/net/ip_vs.h
> @@ -109,7 +109,6 @@ extern int ip_vs_conn_tab_size;
>   struct ip_vs_iphdr {
>   	__u32 len;	/* IPv4 simply where L4 starts
>   			   IPv6 where L4 Transport Header starts */
> -	__u32 thoff_reasm; /* Transport Header Offset in nfct_reasm skb */
>   	__u16 fragoffs; /* IPv6 fragment offset, 0 if first frag (or not frag)*/
>   	__s16 protocol;
>   	__s32 flags;
> @@ -117,34 +116,12 @@ struct ip_vs_iphdr {
>   	union nf_inet_addr daddr;
>   };
>
> -/* Dependency to module: nf_defrag_ipv6 */
> -#if defined(CONFIG_NF_DEFRAG_IPV6) || defined(CONFIG_NF_DEFRAG_IPV6_MODULE)
> -static inline struct sk_buff *skb_nfct_reasm(const struct sk_buff *skb)
> -{
> -	return skb->nfct_reasm;
> -}
> -static inline void *frag_safe_skb_hp(const struct sk_buff *skb, int offset,
> -				      int len, void *buffer,
> -				      const struct ip_vs_iphdr *ipvsh)
> -{
> -	if (unlikely(ipvsh->fragoffs && skb_nfct_reasm(skb)))
> -		return skb_header_pointer(skb_nfct_reasm(skb),
> -					  ipvsh->thoff_reasm, len, buffer);
> -
> -	return skb_header_pointer(skb, offset, len, buffer);
> -}
> -#else
> -static inline struct sk_buff *skb_nfct_reasm(const struct sk_buff *skb)
> -{
> -	return NULL;
> -}
>   static inline void *frag_safe_skb_hp(const struct sk_buff *skb, int offset,
>   				      int len, void *buffer,
>   				      const struct ip_vs_iphdr *ipvsh)
>   {
>   	return skb_header_pointer(skb, offset, len, buffer);
>   }
> -#endif
>
>   static inline void
>   ip_vs_fill_ip4hdr(const void *nh, struct ip_vs_iphdr *iphdr)
> @@ -171,19 +148,12 @@ ip_vs_fill_iph_skb(int af, const struct sk_buff *skb, struct ip_vs_iphdr *iphdr)
>   			(struct ipv6hdr *)skb_network_header(skb);
>   		iphdr->saddr.in6 = iph->saddr;
>   		iphdr->daddr.in6 = iph->daddr;
> -		/* ipv6_find_hdr() updates len, flags, thoff_reasm */
> -		iphdr->thoff_reasm = 0;
> +		/* ipv6_find_hdr() updates len, flags */
>   		iphdr->len	 = 0;
>   		iphdr->flags	 = 0;
>   		iphdr->protocol  = ipv6_find_hdr(skb, &iphdr->len, -1,
>   						 &iphdr->fragoffs,
>   						 &iphdr->flags);
> -		/* get proto from re-assembled packet and it's offset */
> -		if (skb_nfct_reasm(skb))
> -			iphdr->protocol = ipv6_find_hdr(skb_nfct_reasm(skb),
> -							&iphdr->thoff_reasm,
> -							-1, NULL, NULL);
> -
>   	} else
>   #endif
>   	{
> diff --git a/include/net/netfilter/ipv6/nf_defrag_ipv6.h b/include/net/netfilter/ipv6/nf_defrag_ipv6.h
> index 5613412..27666d8 100644
> --- a/include/net/netfilter/ipv6/nf_defrag_ipv6.h
> +++ b/include/net/netfilter/ipv6/nf_defrag_ipv6.h
> @@ -6,9 +6,7 @@ void nf_defrag_ipv6_enable(void);
>   int nf_ct_frag6_init(void);
>   void nf_ct_frag6_cleanup(void);
>   struct sk_buff *nf_ct_frag6_gather(struct sk_buff *skb, u32 user);
> -void nf_ct_frag6_output(unsigned int hooknum, struct sk_buff *skb,
> -			struct net_device *in, struct net_device *out,
> -			int (*okfn)(struct sk_buff *));
> +void nf_ct_frag6_consume_orig(struct sk_buff *skb);
>
>   struct inet_frags_ctl;
>
> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index 3735fad..e55e10a 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -592,9 +592,6 @@ static void skb_release_head_state(struct sk_buff *skb)
>   #if IS_ENABLED(CONFIG_NF_CONNTRACK)
>   	nf_conntrack_put(skb->nfct);
>   #endif
> -#ifdef NET_SKBUFF_NF_DEFRAG_NEEDED
> -	nf_conntrack_put_reasm(skb->nfct_reasm);
> -#endif
>   #ifdef CONFIG_BRIDGE_NETFILTER
>   	nf_bridge_put(skb->nf_bridge);
>   #endif
> diff --git a/net/ipv6/netfilter/nf_conntrack_l3proto_ipv6.c b/net/ipv6/netfilter/nf_conntrack_l3proto_ipv6.c
> index 486545e..4cbc6b2 100644
> --- a/net/ipv6/netfilter/nf_conntrack_l3proto_ipv6.c
> +++ b/net/ipv6/netfilter/nf_conntrack_l3proto_ipv6.c
> @@ -169,64 +169,13 @@ out:
>   	return nf_conntrack_confirm(skb);
>   }
>
> -static unsigned int __ipv6_conntrack_in(struct net *net,
> -					unsigned int hooknum,
> -					struct sk_buff *skb,
> -					const struct net_device *in,
> -					const struct net_device *out,
> -					int (*okfn)(struct sk_buff *))
> -{
> -	struct sk_buff *reasm = skb->nfct_reasm;
> -	const struct nf_conn_help *help;
> -	struct nf_conn *ct;
> -	enum ip_conntrack_info ctinfo;
> -
> -	/* This packet is fragmented and has reassembled packet. */
> -	if (reasm) {
> -		/* Reassembled packet isn't parsed yet ? */
> -		if (!reasm->nfct) {
> -			unsigned int ret;
> -
> -			ret = nf_conntrack_in(net, PF_INET6, hooknum, reasm);
> -			if (ret != NF_ACCEPT)
> -				return ret;
> -		}
> -
> -		/* Conntrack helpers need the entire reassembled packet in the
> -		 * POST_ROUTING hook. In case of unconfirmed connections NAT
> -		 * might reassign a helper, so the entire packet is also
> -		 * required.
> -		 */
> -		ct = nf_ct_get(reasm, &ctinfo);
> -		if (ct != NULL && !nf_ct_is_untracked(ct)) {
> -			help = nfct_help(ct);
> -			if ((help && help->helper) || !nf_ct_is_confirmed(ct)) {
> -				nf_conntrack_get_reasm(reasm);
> -				NF_HOOK_THRESH(NFPROTO_IPV6, hooknum, reasm,
> -					       (struct net_device *)in,
> -					       (struct net_device *)out,
> -					       okfn, NF_IP6_PRI_CONNTRACK + 1);
> -				return NF_DROP_ERR(-ECANCELED);
> -			}
> -		}
> -
> -		nf_conntrack_get(reasm->nfct);
> -		skb->nfct = reasm->nfct;
> -		skb->nfctinfo = reasm->nfctinfo;
> -		return NF_ACCEPT;
> -	}
> -
> -	return nf_conntrack_in(net, PF_INET6, hooknum, skb);
> -}
> -
>   static unsigned int ipv6_conntrack_in(const struct nf_hook_ops *ops,
>   				      struct sk_buff *skb,
>   				      const struct net_device *in,
>   				      const struct net_device *out,
>   				      int (*okfn)(struct sk_buff *))
>   {
> -	return __ipv6_conntrack_in(dev_net(in), ops->hooknum, skb, in, out,
> -				   okfn);
> +	return nf_conntrack_in(dev_net(in), PF_INET6, ops->hooknum, skb);
>   }
>
>   static unsigned int ipv6_conntrack_local(const struct nf_hook_ops *ops,
> @@ -240,8 +189,7 @@ static unsigned int ipv6_conntrack_local(const struct nf_hook_ops *ops,
>   		net_notice_ratelimited("ipv6_conntrack_local: packet too short\n");
>   		return NF_ACCEPT;
>   	}
> -	return __ipv6_conntrack_in(dev_net(out), ops->hooknum, skb, in, out,
> -				   okfn);
> +	return nf_conntrack_in(dev_net(out), PF_INET6, ops->hooknum, skb);
>   }
>
>   static struct nf_hook_ops ipv6_conntrack_ops[] __read_mostly = {
> diff --git a/net/ipv6/netfilter/nf_conntrack_reasm.c b/net/ipv6/netfilter/nf_conntrack_reasm.c
> index 4a25826..767ab8d 100644
> --- a/net/ipv6/netfilter/nf_conntrack_reasm.c
> +++ b/net/ipv6/netfilter/nf_conntrack_reasm.c
> @@ -633,31 +633,16 @@ ret_orig:
>   	return skb;
>   }
>
> -void nf_ct_frag6_output(unsigned int hooknum, struct sk_buff *skb,
> -			struct net_device *in, struct net_device *out,
> -			int (*okfn)(struct sk_buff *))
> +void nf_ct_frag6_consume_orig(struct sk_buff *skb)
>   {
>   	struct sk_buff *s, *s2;
> -	unsigned int ret = 0;
>
>   	for (s = NFCT_FRAG6_CB(skb)->orig; s;) {
> -		nf_conntrack_put_reasm(s->nfct_reasm);
> -		nf_conntrack_get_reasm(skb);
> -		s->nfct_reasm = skb;
> -
>   		s2 = s->next;
>   		s->next = NULL;
> -
> -		if (ret != -ECANCELED)
> -			ret = NF_HOOK_THRESH(NFPROTO_IPV6, hooknum, s,
> -					     in, out, okfn,
> -					     NF_IP6_PRI_CONNTRACK_DEFRAG + 1);
> -		else
> -			kfree_skb(s);
> -
> +		consume_skb(s);
>   		s = s2;
>   	}
> -	nf_conntrack_put_reasm(skb);
>   }
>
>   static int nf_ct_net_init(struct net *net)
> diff --git a/net/ipv6/netfilter/nf_defrag_ipv6_hooks.c b/net/ipv6/netfilter/nf_defrag_ipv6_hooks.c
> index ec483aa..7b9a748 100644
> --- a/net/ipv6/netfilter/nf_defrag_ipv6_hooks.c
> +++ b/net/ipv6/netfilter/nf_defrag_ipv6_hooks.c
> @@ -75,8 +75,11 @@ static unsigned int ipv6_defrag(const struct nf_hook_ops *ops,
>   	if (reasm == skb)
>   		return NF_ACCEPT;
>
> -	nf_ct_frag6_output(ops->hooknum, reasm, (struct net_device *)in,
> -			   (struct net_device *)out, okfn);
> +	nf_ct_frag6_consume_orig(reasm);
> +
> +	NF_HOOK_THRESH(NFPROTO_IPV6, ops->hooknum, reasm,
> +		       (struct net_device *) in, (struct net_device *) out,
> +		       okfn, NF_IP6_PRI_CONNTRACK_DEFRAG + 1);
>
>   	return NF_STOLEN;
>   }
> diff --git a/net/netfilter/ipvs/ip_vs_core.c b/net/netfilter/ipvs/ip_vs_core.c
> index 34fda62..4f26ee4 100644
> --- a/net/netfilter/ipvs/ip_vs_core.c
> +++ b/net/netfilter/ipvs/ip_vs_core.c
> @@ -1139,12 +1139,6 @@ ip_vs_out(unsigned int hooknum, struct sk_buff *skb, int af)
>   	ip_vs_fill_iph_skb(af, skb, &iph);
>   #ifdef CONFIG_IP_VS_IPV6
>   	if (af == AF_INET6) {
> -		if (!iph.fragoffs && skb_nfct_reasm(skb)) {
> -			struct sk_buff *reasm = skb_nfct_reasm(skb);
> -			/* Save fw mark for coming frags */
> -			reasm->ipvs_property = 1;
> -			reasm->mark = skb->mark;
> -		}
>   		if (unlikely(iph.protocol == IPPROTO_ICMPV6)) {
>   			int related;
>   			int verdict = ip_vs_out_icmp_v6(skb, &related,
> @@ -1614,12 +1608,6 @@ ip_vs_in(unsigned int hooknum, struct sk_buff *skb, int af)
>
>   #ifdef CONFIG_IP_VS_IPV6
>   	if (af == AF_INET6) {
> -		if (!iph.fragoffs && skb_nfct_reasm(skb)) {
> -			struct sk_buff *reasm = skb_nfct_reasm(skb);
> -			/* Save fw mark for coming frags. */
> -			reasm->ipvs_property = 1;
> -			reasm->mark = skb->mark;
> -		}
>   		if (unlikely(iph.protocol == IPPROTO_ICMPV6)) {
>   			int related;
>   			int verdict = ip_vs_in_icmp_v6(skb, &related, hooknum,
> @@ -1671,9 +1659,8 @@ ip_vs_in(unsigned int hooknum, struct sk_buff *skb, int af)
>   		/* sorry, all this trouble for a no-hit :) */
>   		IP_VS_DBG_PKT(12, af, pp, skb, 0,
>   			      "ip_vs_in: packet continues traversal as normal");
> -		if (iph.fragoffs && !skb_nfct_reasm(skb)) {
> +		if (iph.fragoffs) {
>   			/* Fragment that couldn't be mapped to a conn entry
> -			 * and don't have any pointer to a reasm skb
>   			 * is missing module nf_defrag_ipv6
>   			 */
>   			IP_VS_DBG_RL("Unhandled frag, load nf_defrag_ipv6\n");
> @@ -1756,38 +1743,6 @@ ip_vs_local_request4(const struct nf_hook_ops *ops, struct sk_buff *skb,
>   #ifdef CONFIG_IP_VS_IPV6
>
>   /*
> - * AF_INET6 fragment handling
> - * Copy info from first fragment, to the rest of them.
> - */
> -static unsigned int
> -ip_vs_preroute_frag6(const struct nf_hook_ops *ops, struct sk_buff *skb,
> -		     const struct net_device *in,
> -		     const struct net_device *out,
> -		     int (*okfn)(struct sk_buff *))
> -{
> -	struct sk_buff *reasm = skb_nfct_reasm(skb);
> -	struct net *net;
> -
> -	/* Skip if not a "replay" from nf_ct_frag6_output or first fragment.
> -	 * ipvs_property is set when checking first fragment
> -	 * in ip_vs_in() and ip_vs_out().
> -	 */
> -	if (reasm)
> -		IP_VS_DBG(2, "Fragment recv prop:%d\n", reasm->ipvs_property);
> -	if (!reasm || !reasm->ipvs_property)
> -		return NF_ACCEPT;
> -
> -	net = skb_net(skb);
> -	if (!net_ipvs(net)->enable)
> -		return NF_ACCEPT;
> -
> -	/* Copy stored fw mark, saved in ip_vs_{in,out} */
> -	skb->mark = reasm->mark;
> -
> -	return NF_ACCEPT;
> -}
> -
> -/*
>    *	AF_INET6 handler in NF_INET_LOCAL_IN chain
>    *	Schedule and forward packets from remote clients
>    */
> @@ -1924,14 +1879,6 @@ static struct nf_hook_ops ip_vs_ops[] __read_mostly = {
>   		.priority	= 100,
>   	},
>   #ifdef CONFIG_IP_VS_IPV6
> -	/* After mangle & nat fetch 2:nd fragment and following */
> -	{
> -		.hook		= ip_vs_preroute_frag6,
> -		.owner		= THIS_MODULE,
> -		.pf		= NFPROTO_IPV6,
> -		.hooknum	= NF_INET_PRE_ROUTING,
> -		.priority	= NF_IP6_PRI_NAT_DST + 1,
> -	},
>   	/* After packet filtering, change source only for VS/NAT */
>   	{
>   		.hook		= ip_vs_reply6,
> diff --git a/net/netfilter/ipvs/ip_vs_pe_sip.c b/net/netfilter/ipvs/ip_vs_pe_sip.c
> index 9ef22bd..bed5f70 100644
> --- a/net/netfilter/ipvs/ip_vs_pe_sip.c
> +++ b/net/netfilter/ipvs/ip_vs_pe_sip.c
> @@ -65,7 +65,6 @@ static int get_callid(const char *dptr, unsigned int dataoff,
>   static int
>   ip_vs_sip_fill_param(struct ip_vs_conn_param *p, struct sk_buff *skb)
>   {
> -	struct sk_buff *reasm = skb_nfct_reasm(skb);
>   	struct ip_vs_iphdr iph;
>   	unsigned int dataoff, datalen, matchoff, matchlen;
>   	const char *dptr;
> @@ -79,15 +78,10 @@ ip_vs_sip_fill_param(struct ip_vs_conn_param *p, struct sk_buff *skb)
>   	/* todo: IPv6 fragments:
>   	 *       I think this only should be done for the first fragment. /HS
>   	 */
> -	if (reasm) {
> -		skb = reasm;
> -		dataoff = iph.thoff_reasm + sizeof(struct udphdr);
> -	} else
> -		dataoff = iph.len + sizeof(struct udphdr);
> +	dataoff = iph.len + sizeof(struct udphdr);
>
>   	if (dataoff >= skb->len)
>   		return -EINVAL;
> -	/* todo: Check if this will mess-up the reasm skb !!! /HS */
>   	retc = skb_linearize(skb);
>   	if (retc < 0)
>   		return retc;
>