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Re: [PATCH] ipvs: fix problems with active FTP

To: Julian Anastasov <ja@xxxxxx>
Subject: Re: [PATCH] ipvs: fix problems with active FTP
Cc: lvs-devel@xxxxxxxxxxxxxxx, netfilter-devel <netfilter-devel@xxxxxxxxxxxxxxx>
From: Simon Horman <horms@xxxxxxxxxxxx>
Date: Thu, 2 Sep 2010 10:54:42 +0900
On Thu, Sep 02, 2010 at 02:41:35AM +0300, Julian Anastasov wrote:
> 
>       Fix Active FTP:
> 
> - Do not create expectation when forwarding the PORT
> command to avoid blocking the connection. The problem is that
> nf_conntrack_ftp.c:help() tries to create the same expectation
> later in POST_ROUTING and drops the packet with "dropping packet"
> message after failure in nf_ct_expect_related.
> 
> - Change ip_vs_update_conntrack to alter the conntrack
> for related connections from real server. If we do not alter
> the reply in this direction the next packet from client
> sent to vport 20 comes as NEW connection. We alter it
> but may be some collision happens for both conntracks and
> the second conntrack gets destroyed immediately. The connection
> stucks too.
> 
> Signed-off-by: Julian Anastasov <ja@xxxxxx>
> ---

Thanks, this looks good to me. I have CCed the netfilter-devel
list for review there.

> 
>       This patch is for 2.6.36
> 
> diff -urp v2.6.36-rc2/linux/include/net/ip_vs.h linux/include/net/ip_vs.h
> --- v2.6.36-rc2/linux/include/net/ip_vs.h     2010-08-26 09:11:45.000000000 
> +0300
> +++ linux/include/net/ip_vs.h 2010-09-02 01:10:31.000000000 +0300
> @@ -955,6 +955,9 @@ static inline __wsum ip_vs_check_diff2(_
>       return csum_partial(diff, sizeof(diff), oldsum);
>  }
>  
> +extern void ip_vs_update_conntrack(struct sk_buff *skb, struct ip_vs_conn 
> *cp,
> +                                int outin);
> +
>  #endif /* __KERNEL__ */
>  
>  #endif       /* _NET_IP_VS_H */
> diff -urp v2.6.36-rc2/linux/net/netfilter/ipvs/ip_vs_core.c 
> linux/net/netfilter/ipvs/ip_vs_core.c
> --- v2.6.36-rc2/linux/net/netfilter/ipvs/ip_vs_core.c 2010-08-26 
> 09:11:47.000000000 +0300
> +++ linux/net/netfilter/ipvs/ip_vs_core.c     2010-09-02 01:08:36.000000000 
> +0300
> @@ -924,6 +924,7 @@ handle_response(int af, struct sk_buff *
>  
>       ip_vs_out_stats(cp, skb);
>       ip_vs_set_state(cp, IP_VS_DIR_OUTPUT, skb, pp);
> +     ip_vs_update_conntrack(skb, cp, 0);
>       ip_vs_conn_put(cp);
>  
>       skb->ipvs_property = 1;
> diff -urp v2.6.36-rc2/linux/net/netfilter/ipvs/ip_vs_ftp.c 
> linux/net/netfilter/ipvs/ip_vs_ftp.c
> --- v2.6.36-rc2/linux/net/netfilter/ipvs/ip_vs_ftp.c  2010-08-26 
> 09:11:47.000000000 +0300
> +++ linux/net/netfilter/ipvs/ip_vs_ftp.c      2010-09-02 00:45:54.000000000 
> +0300
> @@ -409,7 +409,6 @@ static int ip_vs_ftp_in(struct ip_vs_app
>       union nf_inet_addr to;
>       __be16 port;
>       struct ip_vs_conn *n_cp;
> -     struct nf_conn *ct;
>  
>  #ifdef CONFIG_IP_VS_IPV6
>       /* This application helper doesn't work with IPv6 yet,
> @@ -496,11 +495,6 @@ static int ip_vs_ftp_in(struct ip_vs_app
>               ip_vs_control_add(n_cp, cp);
>       }
>  
> -     ct = (struct nf_conn *)skb->nfct;
> -     if (ct && ct != &nf_conntrack_untracked)
> -             ip_vs_expect_related(skb, ct, n_cp,
> -                                  IPPROTO_TCP, &n_cp->dport, 1);
> -
>       /*
>        *      Move tunnel to listen state
>        */
> diff -urp v2.6.36-rc2/linux/net/netfilter/ipvs/ip_vs_xmit.c 
> linux/net/netfilter/ipvs/ip_vs_xmit.c
> --- v2.6.36-rc2/linux/net/netfilter/ipvs/ip_vs_xmit.c 2010-08-26 
> 09:11:47.000000000 +0300
> +++ linux/net/netfilter/ipvs/ip_vs_xmit.c     2010-09-02 01:04:16.000000000 
> +0300
> @@ -349,8 +349,8 @@ ip_vs_bypass_xmit_v6(struct sk_buff *skb
>  }
>  #endif
>  
> -static void
> -ip_vs_update_conntrack(struct sk_buff *skb, struct ip_vs_conn *cp)
> +void
> +ip_vs_update_conntrack(struct sk_buff *skb, struct ip_vs_conn *cp, int outin)
>  {
>       struct nf_conn *ct = (struct nf_conn *)skb->nfct;
>       struct nf_conntrack_tuple new_tuple;
> @@ -365,11 +365,17 @@ ip_vs_update_conntrack(struct sk_buff *s
>        * real-server we will see RIP->DIP.
>        */
>       new_tuple = ct->tuplehash[IP_CT_DIR_REPLY].tuple;
> -     new_tuple.src.u3 = cp->daddr;
> +     if (outin)
> +             new_tuple.src.u3 = cp->daddr;
> +     else
> +             new_tuple.dst.u3 = cp->vaddr;
>       /*
>        * This will also take care of UDP and other protocols.
>        */
> -     new_tuple.src.u.tcp.port = cp->dport;
> +     if (outin)
> +             new_tuple.src.u.tcp.port = cp->dport;
> +     else
> +             new_tuple.dst.u.tcp.port = cp->vport;
>       nf_conntrack_alter_reply(ct, &new_tuple);
>  }
>  
> @@ -428,7 +434,7 @@ ip_vs_nat_xmit(struct sk_buff *skb, stru
>  
>       IP_VS_DBG_PKT(10, pp, skb, 0, "After DNAT");
>  
> -     ip_vs_update_conntrack(skb, cp);
> +     ip_vs_update_conntrack(skb, cp, 1);
>  
>       /* FIXME: when application helper enlarges the packet and the length
>          is larger than the MTU of outgoing device, there will be still
> @@ -506,7 +512,7 @@ ip_vs_nat_xmit_v6(struct sk_buff *skb, s
>  
>       IP_VS_DBG_PKT(10, pp, skb, 0, "After DNAT");
>  
> -     ip_vs_update_conntrack(skb, cp);
> +     ip_vs_update_conntrack(skb, cp, 1);
>  
>       /* FIXME: when application helper enlarges the packet and the length
>          is larger than the MTU of outgoing device, there will be still
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