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Re: [patch v2] ipvs: IPv6 tunnel mode

To: Simon Horman <horms@xxxxxxxxxxxx>
Subject: Re: [patch v2] ipvs: IPv6 tunnel mode
Cc: Julian Anastasov <ja@xxxxxx>, "lvs-devel@xxxxxxxxxxxxxxx" <lvs-devel@xxxxxxxxxxxxxxx>, Julius Volz <juliusv@xxxxxxxxxx>
From: Hans Schillstrom <hans.schillstrom@xxxxxxxxxxxx>
Date: Mon, 27 Sep 2010 08:00:54 +0200
Hello,

On Sun, 2010-09-26 at 15:33 +0200, Simon Horman wrote:
> From: Julian Anastasov <ja@xxxxxx>
> 
> Tunnel mode for IPv6 doesn't work.
> 
> IPv6 encapsulation uses a bad source address for the tunnel.
> i.e. VIP will be used as local-addr and encap. dst addr.
> Decapsulation will not accept this.
> 
> Example
> LVS (eth1 2003::2:0:1/96, VIP 2003::2:0:100)
>    (eth0 2003::1:0:1/96)
> RS  (ethX 2003::1:0:5/96)
> 
> tcpdump
> 2003::2:0:100 > 2003::1:0:5:
> IP6 (hlim 63, next-header TCP (6) payload length: 40)
>  2003::3:0:10.50991 > 2003::2:0:100.http: Flags [S], cksum 0x7312
> (correct), seq 3006460279, win 5760, options [mss 1440,sackOK,TS val
> 1904932 ecr 0,nop,wscale 3], length 0
> 
> In Linux IPv6 impl. you can't have a tunnel with an any cast address
> receiving packets (I have not tried to interpret RFC 2473)
> To have receive capabilities the tunnel must have:
>  - Local address set as multicast addr or an unicast addr
>  - Remote address set as an unicast addr.
>  - Loop back addres or Link local address are not allowed.
> 
> This causes us to setup a tunnel in the Real Server with the
> LVS as the remote address, here you can't use the VIP address since it's
> used inside the tunnel.
> 
> Solution
> Use outgoing interface IPv6 address (match against the destination).
> i.e. use ip6_route_output() to look up the route cache and
> then use ipv6_dev_get_saddr(...) to set the source address of the
> encapsulated packet.
> 
> Additionally, cache the results in new destination
> fields: dst_cookie and dst_saddr and properly check the
> returned dst from ip6_route_output. We now add xfrm_lookup
> call only for the tunneling method where the source address
> is a local one.
> 
> Original patch by Hans Schillstrom.
> Check dst state and cache results for IPv6 by Julian Anastasov.
> 
> Tested-by: Hans Schillstrom <hans.schillstrom@xxxxxxxxxxxx>
> Signed-off-by: Julian Anastasov <ja@xxxxxx>
> Signed-off-by: Simon Horman <horms@xxxxxxxxxxxx>
> 
> ---
> 
> * v1
> 
>   This is Julian's patch with a slightly edited version of the description
>   from Hans's original patch.
> 
> * v2
> 
>   Updated changelog as per commends from Julian
> 
> Is everyone ok with pushing this?
> 
> diff -urp net-next-2.6-e548833-nfct_snat_reroute/linux/include/net/ip_vs.h 
> linux/include/net/ip_vs.h
> --- net-next-2.6-e548833-nfct_snat_reroute/linux/include/net/ip_vs.h    
> 2010-09-16 09:03:48.000000000 +0300
> +++ linux/include/net/ip_vs.h   2010-09-22 10:50:18.548963467 +0300
> @@ -509,6 +509,10 @@ struct ip_vs_dest {
>         spinlock_t              dst_lock;       /* lock of dst_cache */
>         struct dst_entry        *dst_cache;     /* destination cache entry */
>         u32                     dst_rtos;       /* RT_TOS(tos) for dst */
> +       u32                     dst_cookie;
> +#ifdef CONFIG_IP_VS_IPV6
> +       struct in6_addr         dst_saddr;
> +#endif
> 
>         /* for virtual service */
>         struct ip_vs_service    *svc;           /* service it belongs to */
> diff -urp 
> net-next-2.6-e548833-nfct_snat_reroute/linux/net/netfilter/ipvs/ip_vs_xmit.c 
> linux/net/netfilter/ipvs/ip_vs_xmit.c
> --- 
> net-next-2.6-e548833-nfct_snat_reroute/linux/net/netfilter/ipvs/ip_vs_xmit.c  
>       2010-09-16 09:02:25.000000000 +0300
> +++ linux/net/netfilter/ipvs/ip_vs_xmit.c       2010-09-22 16:29:43.271964521 
> +0300
> @@ -26,6 +26,7 @@
>  #include <net/route.h>                  /* for ip_route_output */
>  #include <net/ipv6.h>
>  #include <net/ip6_route.h>
> +#include <net/addrconf.h>
>  #include <linux/icmpv6.h>
>  #include <linux/netfilter.h>
>  #include <linux/netfilter_ipv4.h>
> @@ -37,26 +38,27 @@
>   *      Destination cache to speed up outgoing route lookup
>   */
>  static inline void
> -__ip_vs_dst_set(struct ip_vs_dest *dest, u32 rtos, struct dst_entry *dst)
> +__ip_vs_dst_set(struct ip_vs_dest *dest, u32 rtos, struct dst_entry *dst,
> +               u32 dst_cookie)
>  {
>         struct dst_entry *old_dst;
> 
>         old_dst = dest->dst_cache;
>         dest->dst_cache = dst;
>         dest->dst_rtos = rtos;
> +       dest->dst_cookie = dst_cookie;
>         dst_release(old_dst);
>  }
> 
>  static inline struct dst_entry *
> -__ip_vs_dst_check(struct ip_vs_dest *dest, u32 rtos, u32 cookie)
> +__ip_vs_dst_check(struct ip_vs_dest *dest, u32 rtos)
>  {
>         struct dst_entry *dst = dest->dst_cache;
> 
>         if (!dst)
>                 return NULL;
> -       if ((dst->obsolete
> -            || (dest->af == AF_INET && rtos != dest->dst_rtos)) &&
> -           dst->ops->check(dst, cookie) == NULL) {
> +       if ((dst->obsolete || rtos != dest->dst_rtos) &&
> +           dst->ops->check(dst, dest->dst_cookie) == NULL) {
>                 dest->dst_cache = NULL;
>                 dst_release(dst);
>                 return NULL;
> @@ -66,15 +68,16 @@ __ip_vs_dst_check(struct ip_vs_dest *des
>  }
> 
>  static struct rtable *
> -__ip_vs_get_out_rt(struct ip_vs_conn *cp, u32 rtos)
> +__ip_vs_get_out_rt(struct sk_buff *skb, struct ip_vs_conn *cp, u32 rtos)
>  {
> +       struct net *net = dev_net(skb->dev);
>         struct rtable *rt;                      /* Route to the other host */
>         struct ip_vs_dest *dest = cp->dest;
> 
>         if (dest) {
>                 spin_lock(&dest->dst_lock);
>                 if (!(rt = (struct rtable *)
> -                     __ip_vs_dst_check(dest, rtos, 0))) {
> +                     __ip_vs_dst_check(dest, rtos))) {
>                         struct flowi fl = {
>                                 .oif = 0,
>                                 .nl_u = {
> @@ -84,13 +87,13 @@ __ip_vs_get_out_rt(struct ip_vs_conn *cp
>                                                 .tos = rtos, } },
>                         };
> 
> -                       if (ip_route_output_key(&init_net, &rt, &fl)) {
> +                       if (ip_route_output_key(net, &rt, &fl)) {
>                                 spin_unlock(&dest->dst_lock);
>                                 IP_VS_DBG_RL("ip_route_output error, dest: 
> %pI4\n",
>                                              &dest->addr.ip);
>                                 return NULL;
>                         }
> -                       __ip_vs_dst_set(dest, rtos, dst_clone(&rt->dst));
> +                       __ip_vs_dst_set(dest, rtos, dst_clone(&rt->dst), 0);
>                         IP_VS_DBG(10, "new dst %pI4, refcnt=%d, rtos=%X\n",
>                                   &dest->addr.ip,
>                                   atomic_read(&rt->dst.__refcnt), rtos);
> @@ -106,7 +109,7 @@ __ip_vs_get_out_rt(struct ip_vs_conn *cp
>                                         .tos = rtos, } },
>                 };
> 
> -               if (ip_route_output_key(&init_net, &rt, &fl)) {
> +               if (ip_route_output_key(net, &rt, &fl)) {
>                         IP_VS_DBG_RL("ip_route_output error, dest: %pI4\n",
>                                      &cp->daddr.ip);
>                         return NULL;
> @@ -117,62 +120,79 @@ __ip_vs_get_out_rt(struct ip_vs_conn *cp
>  }
> 
>  #ifdef CONFIG_IP_VS_IPV6
> +
> +static struct dst_entry *
> +__ip_vs_route_output_v6(struct net *net, struct in6_addr *daddr,
> +                       struct in6_addr *ret_saddr, int do_xfrm)
> +{
> +       struct dst_entry *dst;
> +       struct flowi fl = {
> +               .oif = 0,
> +               .nl_u = {
> +                       .ip6_u = {
> +                               .daddr = *daddr,
> +                       },
> +               },
> +       };
> +
> +       dst = ip6_route_output(net, NULL, &fl);
> +       if (dst->error)
> +               goto out_err;
> +       if (!ret_saddr)
> +               return dst;
> +       if (ipv6_addr_any(&fl.fl6_src) &&
> +           ipv6_dev_get_saddr(net, ip6_dst_idev(dst)->dev,
> +                              &fl.fl6_dst, 0, &fl.fl6_src) < 0)
> +               goto out_err;
> +       if (do_xfrm && xfrm_lookup(net, &dst, &fl, NULL, 0) < 0)
> +               goto out_err;
> +       ipv6_addr_copy(ret_saddr, &fl.fl6_src);
> +       return dst;
> +
> +out_err:
> +       dst_release(dst);
> +       IP_VS_DBG_RL("ip6_route_output error, dest: %pI6\n", daddr);
> +       return NULL;
> +}
> +
>  static struct rt6_info *
> -__ip_vs_get_out_rt_v6(struct ip_vs_conn *cp)
> +__ip_vs_get_out_rt_v6(struct sk_buff *skb, struct ip_vs_conn *cp,
> +                     struct in6_addr *ret_saddr, int do_xfrm)
>  {
> +       struct net *net = dev_net(skb->dev);
>         struct rt6_info *rt;                    /* Route to the other host */
>         struct ip_vs_dest *dest = cp->dest;
> +       struct dst_entry *dst;
> 
>         if (dest) {
>                 spin_lock(&dest->dst_lock);
> -               rt = (struct rt6_info *)__ip_vs_dst_check(dest, 0, 0);
> +               rt = (struct rt6_info *)__ip_vs_dst_check(dest, 0);
>                 if (!rt) {
> -                       struct flowi fl = {
> -                               .oif = 0,
> -                               .nl_u = {
> -                                       .ip6_u = {
> -                                               .daddr = dest->addr.in6,
> -                                               .saddr = {
> -                                                       .s6_addr32 =
> -                                                               { 0, 0, 0, 0 
> },
> -                                               },
> -                                       },
> -                               },
> -                       };
> +                       u32 cookie;
> 
> -                       rt = (struct rt6_info *)ip6_route_output(&init_net,
> -                                                                NULL, &fl);
> -                       if (!rt) {
> +                       dst = __ip_vs_route_output_v6(net, &dest->addr.in6,
> +                                                     &dest->dst_saddr,
> +                                                     do_xfrm);
> +                       if (!dst) {
>                                 spin_unlock(&dest->dst_lock);
> -                               IP_VS_DBG_RL("ip6_route_output error, dest: 
> %pI6\n",
> -                                            &dest->addr.in6);
>                                 return NULL;
>                         }
> -                       __ip_vs_dst_set(dest, 0, dst_clone(&rt->dst));
> -                       IP_VS_DBG(10, "new dst %pI6, refcnt=%d\n",
> -                                 &dest->addr.in6,
> +                       rt = (struct rt6_info *) dst;
> +                       cookie = rt->rt6i_node ? rt->rt6i_node->fn_sernum : 0;
> +                       __ip_vs_dst_set(dest, 0, dst_clone(&rt->dst), cookie);
> +                       IP_VS_DBG(10, "new dst %pI6, src %pI6, refcnt=%d\n",
> +                                 &dest->addr.in6, &dest->dst_saddr,
>                                   atomic_read(&rt->dst.__refcnt));
>                 }
> +               if (ret_saddr)
> +                       ipv6_addr_copy(ret_saddr, &dest->dst_saddr);
>                 spin_unlock(&dest->dst_lock);
>         } else {
> -               struct flowi fl = {
> -                       .oif = 0,
> -                       .nl_u = {
> -                               .ip6_u = {
> -                                       .daddr = cp->daddr.in6,
> -                                       .saddr = {
> -                                               .s6_addr32 = { 0, 0, 0, 0 },
> -                                       },
> -                               },
> -                       },
> -               };
> -
> -               rt = (struct rt6_info *)ip6_route_output(&init_net, NULL, 
> &fl);
> -               if (!rt) {
> -                       IP_VS_DBG_RL("ip6_route_output error, dest: %pI6\n",
> -                                    &cp->daddr.in6);
> +               dst = __ip_vs_route_output_v6(net, &cp->daddr.in6, ret_saddr,
> +                                             do_xfrm);
> +               if (!dst)
>                         return NULL;
> -               }
> +               rt = (struct rt6_info *) dst;
>         }
> 
>         return rt;
> @@ -248,6 +268,7 @@ int
>  ip_vs_bypass_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
>                   struct ip_vs_protocol *pp)
>  {
> +       struct net *net = dev_net(skb->dev);
>         struct rtable *rt;                      /* Route to the other host */
>         struct iphdr  *iph = ip_hdr(skb);
>         u8     tos = iph->tos;
> @@ -263,7 +284,7 @@ ip_vs_bypass_xmit(struct sk_buff *skb, s
> 
>         EnterFunction(10);
> 
> -       if (ip_route_output_key(&init_net, &rt, &fl)) {
> +       if (ip_route_output_key(net, &rt, &fl)) {
>                 IP_VS_DBG_RL("%s(): ip_route_output error, dest: %pI4\n",
>                              __func__, &iph->daddr);
>                 goto tx_error_icmp;
> @@ -313,25 +334,18 @@ int
>  ip_vs_bypass_xmit_v6(struct sk_buff *skb, struct ip_vs_conn *cp,
>                      struct ip_vs_protocol *pp)
>  {
> +       struct net *net = dev_net(skb->dev);
> +       struct dst_entry *dst;
>         struct rt6_info *rt;                    /* Route to the other host */
>         struct ipv6hdr  *iph = ipv6_hdr(skb);
>         int    mtu;
> -       struct flowi fl = {
> -               .oif = 0,
> -               .nl_u = {
> -                       .ip6_u = {
> -                               .daddr = iph->daddr,
> -                               .saddr = { .s6_addr32 = {0, 0, 0, 0} }, } },
> -       };
> 
>         EnterFunction(10);
> 
> -       rt = (struct rt6_info *)ip6_route_output(&init_net, NULL, &fl);
> -       if (!rt) {
> -               IP_VS_DBG_RL("%s(): ip6_route_output error, dest: %pI6\n",
> -                            __func__, &iph->daddr);
> +       dst = __ip_vs_route_output_v6(net, &iph->daddr, NULL, 0);
> +       if (!dst)
>                 goto tx_error_icmp;
> -       }
> +       rt = (struct rt6_info *) dst;
> 
>         /* MTU checking */
>         mtu = dst_mtu(&rt->dst);
> @@ -397,7 +411,7 @@ ip_vs_nat_xmit(struct sk_buff *skb, stru
>                 IP_VS_DBG(10, "filled cport=%d\n", ntohs(*p));
>         }
> 
> -       if (!(rt = __ip_vs_get_out_rt(cp, RT_TOS(iph->tos))))
> +       if (!(rt = __ip_vs_get_out_rt(skb, cp, RT_TOS(iph->tos))))
>                 goto tx_error_icmp;
> 
>         /* MTU checking */
> @@ -472,7 +486,7 @@ ip_vs_nat_xmit_v6(struct sk_buff *skb, s
>                 IP_VS_DBG(10, "filled cport=%d\n", ntohs(*p));
>         }
> 
> -       rt = __ip_vs_get_out_rt_v6(cp);
> +       rt = __ip_vs_get_out_rt_v6(skb, cp, NULL, 0);
>         if (!rt)
>                 goto tx_error_icmp;
> 
> @@ -557,7 +571,6 @@ ip_vs_tunnel_xmit(struct sk_buff *skb, s
>         struct iphdr  *old_iph = ip_hdr(skb);
>         u8     tos = old_iph->tos;
>         __be16 df = old_iph->frag_off;
> -       sk_buff_data_t old_transport_header = skb->transport_header;
>         struct iphdr  *iph;                     /* Our new IP header */
>         unsigned int max_headroom;              /* The extra header space 
> needed */
>         int    mtu;
> @@ -572,7 +585,7 @@ ip_vs_tunnel_xmit(struct sk_buff *skb, s
>                 goto tx_error;
>         }
> 
> -       if (!(rt = __ip_vs_get_out_rt(cp, RT_TOS(tos))))
> +       if (!(rt = __ip_vs_get_out_rt(skb, cp, RT_TOS(tos))))
>                 goto tx_error_icmp;
> 
>         tdev = rt->dst.dev;
> @@ -616,7 +629,7 @@ ip_vs_tunnel_xmit(struct sk_buff *skb, s
>                 old_iph = ip_hdr(skb);
>         }
> 
> -       skb->transport_header = old_transport_header;
> +       skb->transport_header = skb->network_header;
> 
>         /* fix old IP header checksum */
>         ip_send_check(old_iph);
> @@ -670,9 +683,9 @@ ip_vs_tunnel_xmit_v6(struct sk_buff *skb
>                      struct ip_vs_protocol *pp)
>  {
>         struct rt6_info *rt;            /* Route to the other host */
> +       struct in6_addr saddr;          /* Source for tunnel */
>         struct net_device *tdev;        /* Device to other host */
>         struct ipv6hdr  *old_iph = ipv6_hdr(skb);
> -       sk_buff_data_t old_transport_header = skb->transport_header;
>         struct ipv6hdr  *iph;           /* Our new IP header */
>         unsigned int max_headroom;      /* The extra header space needed */
>         int    mtu;
> @@ -687,17 +700,17 @@ ip_vs_tunnel_xmit_v6(struct sk_buff *skb
>                 goto tx_error;
>         }
> 
> -       rt = __ip_vs_get_out_rt_v6(cp);
> +       rt = __ip_vs_get_out_rt_v6(skb, cp, &saddr, 1);
>         if (!rt)
>                 goto tx_error_icmp;
> 
>         tdev = rt->dst.dev;
> 
>         mtu = dst_mtu(&rt->dst) - sizeof(struct ipv6hdr);
> -       /* TODO IPv6: do we need this check in IPv6? */
> -       if (mtu < 1280) {
> +       if (mtu < IPV6_MIN_MTU) {
>                 dst_release(&rt->dst);
> -               IP_VS_DBG_RL("%s(): mtu less than 1280\n", __func__);
> +               IP_VS_DBG_RL("%s(): mtu less than %d\n", __func__,
> +                            IPV6_MIN_MTU);
>                 goto tx_error;
>         }
>         if (skb_dst(skb))
> @@ -730,7 +743,7 @@ ip_vs_tunnel_xmit_v6(struct sk_buff *skb
>                 old_iph = ipv6_hdr(skb);
>         }
> 
> -       skb->transport_header = old_transport_header;
> +       skb->transport_header = skb->network_header;
> 
>         skb_push(skb, sizeof(struct ipv6hdr));
>         skb_reset_network_header(skb);
> @@ -750,8 +763,8 @@ ip_vs_tunnel_xmit_v6(struct sk_buff *skb
>         be16_add_cpu(&iph->payload_len, sizeof(*old_iph));
>         iph->priority           =       old_iph->priority;
>         memset(&iph->flow_lbl, 0, sizeof(iph->flow_lbl));
> -       iph->daddr              =       rt->rt6i_dst.addr;
> -       iph->saddr              =       cp->vaddr.in6; /* rt->rt6i_src.addr; 
> */
> +       ipv6_addr_copy(&iph->daddr, &rt->rt6i_dst.addr);
> +       ipv6_addr_copy(&iph->saddr, &saddr);
>         iph->hop_limit          =       old_iph->hop_limit;
> 
>         /* Another hack: avoid icmp_send in ip_fragment */
> @@ -791,7 +804,7 @@ ip_vs_dr_xmit(struct sk_buff *skb, struc
> 
>         EnterFunction(10);
> 
> -       if (!(rt = __ip_vs_get_out_rt(cp, RT_TOS(iph->tos))))
> +       if (!(rt = __ip_vs_get_out_rt(skb, cp, RT_TOS(iph->tos))))
>                 goto tx_error_icmp;
> 
>         /* MTU checking */
> @@ -843,7 +856,7 @@ ip_vs_dr_xmit_v6(struct sk_buff *skb, st
> 
>         EnterFunction(10);
> 
> -       rt = __ip_vs_get_out_rt_v6(cp);
> +       rt = __ip_vs_get_out_rt_v6(skb, cp, NULL, 0);
>         if (!rt)
>                 goto tx_error_icmp;
> 
> @@ -919,7 +932,7 @@ ip_vs_icmp_xmit(struct sk_buff *skb, str
>          * mangle and send the packet here (only for VS/NAT)
>          */
> 
> -       if (!(rt = __ip_vs_get_out_rt(cp, RT_TOS(ip_hdr(skb)->tos))))
> +       if (!(rt = __ip_vs_get_out_rt(skb, cp, RT_TOS(ip_hdr(skb)->tos))))
>                 goto tx_error_icmp;
> 
>         /* MTU checking */
> @@ -993,7 +1006,7 @@ ip_vs_icmp_xmit_v6(struct sk_buff *skb,
>          * mangle and send the packet here (only for VS/NAT)
>          */
> 
> -       rt = __ip_vs_get_out_rt_v6(cp);
> +       rt = __ip_vs_get_out_rt_v6(skb, cp, NULL, 0);
>         if (!rt)
>                 goto tx_error_icmp;
> 
Looks good, go ahead
--
Regards
Hans Schillstrom <hans.schillstrom@xxxxxxxxxxxx>

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