The objective we have is to remove the fl_net field from the struct flowi.

In the previous patch, we make the network namespace to go up to the dst_entry.
This patch makes an example in how we can use the dst_entry/rtable combined with
a container_of to retrieve the network namespace when we have the flowi 
parameter.

One restriction is we should pass always a flowi parameter coming from a struct
dst_entry.

---
 include/net/ip_fib.h |    3 -
 net/ipv4/route.c     |  111 ++++++++++++++++++++++++++-------------------------
 2 files changed, 60 insertions(+), 54 deletions(-)

Index: linux-2.6-netns/net/ipv4/route.c
===================================================================
--- linux-2.6-netns.orig/net/ipv4/route.c
+++ linux-2.6-netns/net/ipv4/route.c
@@ -1788,15 +1788,18 @@ static int ip_route_input_slow(struct sk
        struct net *net = dev->nd_net;
        struct fib_result res;
        struct in_device *in_dev = in_dev_get(dev);
-       struct flowi fl = { .fl_net = net,
-                           .nl_u = { .ip4_u =
-                                     { .daddr = daddr,
-                                       .saddr = saddr,
-                                       .tos = tos,
-                                       .scope = RT_SCOPE_UNIVERSE,
-                                     } },
-                           .mark = skb->mark,
-                           .iif = dev->ifindex };
+       struct rtable rt = {
+               .u.dst.net = net,
+               .fl = { .fl_net = net,
+                       .nl_u = { .ip4_u =
+                                 { .daddr = daddr,
+                                   .saddr = saddr,
+                                   .tos = tos,
+                                   .scope = RT_SCOPE_UNIVERSE,
+                                 } },
+                       .mark = skb->mark,
+                       .iif = dev->ifindex },
+       };
        unsigned        flags = 0;
        u32             itag = 0;
        struct rtable * rth;
@@ -1832,7 +1835,7 @@ static int ip_route_input_slow(struct sk
        /*
         *      Now we are ready to route packet.
         */
-       if ((err = fib_lookup(&fl, &res)) != 0) {
+       if ((err = fib_lookup(&rt.fl, &res)) != 0) {
                if (!IN_DEV_FORWARD(in_dev))
                        goto e_hostunreach;
                goto no_route;
@@ -1862,7 +1865,7 @@ static int ip_route_input_slow(struct sk
        if (res.type != RTN_UNICAST)
                goto martian_destination;
 
-       err = ip_mkroute_input(skb, &res, &fl, in_dev, daddr, saddr, tos);
+       err = ip_mkroute_input(skb, &res, &rt.fl, in_dev, daddr, saddr, tos);
 done:
        in_dev_put(in_dev);
        if (free_res)
@@ -1898,7 +1901,6 @@ local_input:
        rth->u.dst.flags= DST_HOST;
        if (IN_DEV_CONF_GET(in_dev, NOPOLICY))
                rth->u.dst.flags |= DST_NOPOLICY;
-       rth->fl.fl_net  = net;
        rth->fl.fl4_dst = daddr;
        rth->rt_dst     = daddr;
        rth->fl.fl4_tos = tos;
@@ -1923,7 +1925,7 @@ local_input:
                rth->rt_flags   &= ~RTCF_LOCAL;
        }
        rth->rt_type    = res.type;
-       hash = rt_hash(daddr, saddr, fl.iif);
+       hash = rt_hash(daddr, saddr, rt.fl.iif);
        err = rt_intern_hash(hash, rth, (struct rtable**)&skb->dst);
        goto done;
 
@@ -2173,18 +2175,21 @@ static int ip_route_output_slow(struct r
 {
        u32 tos = RT_FL_TOS(oldflp);
        struct net *net = oldflp->fl_net;
-       struct flowi fl = { .fl_net = net,
-                           .nl_u = { .ip4_u =
-                                     { .daddr = oldflp->fl4_dst,
-                                       .saddr = oldflp->fl4_src,
-                                       .tos = tos & IPTOS_RT_MASK,
-                                       .scope = ((tos & RTO_ONLINK) ?
-                                                 RT_SCOPE_LINK :
-                                                 RT_SCOPE_UNIVERSE),
-                                     } },
-                           .mark = oldflp->mark,
-                           .iif = net->loopback_dev->ifindex,
-                           .oif = oldflp->oif };
+       struct rtable rt = {
+               .u.dst.net = net,
+               .fl = { .fl_net = net,
+                       .nl_u = { .ip4_u =
+                                 { .daddr = oldflp->fl4_dst,
+                                   .saddr = oldflp->fl4_src,
+                                   .tos = tos & IPTOS_RT_MASK,
+                                   .scope = ((tos & RTO_ONLINK) ?
+                                             RT_SCOPE_LINK :
+                                             RT_SCOPE_UNIVERSE),
+                                 } },
+                       .mark = oldflp->mark,
+                       .iif = net->loopback_dev->ifindex,
+                       .oif = oldflp->oif },
+       };
        struct fib_result res;
        unsigned flags = 0;
        struct net_device *dev_out = NULL;
@@ -2234,7 +2239,7 @@ static int ip_route_output_slow(struct r
                           Luckily, this hack is good workaround.
                         */
 
-                       fl.oif = dev_out->ifindex;
+                       rt.fl.oif = dev_out->ifindex;
                        goto make_route;
                }
                if (dev_out)
@@ -2256,36 +2261,36 @@ static int ip_route_output_slow(struct r
                }
 
                if (LOCAL_MCAST(oldflp->fl4_dst) || oldflp->fl4_dst == 
htonl(0xFFFFFFFF)) {
-                       if (!fl.fl4_src)
-                               fl.fl4_src = inet_select_addr(dev_out, 0,
-                                                             RT_SCOPE_LINK);
+                       if (!rt.fl.fl4_src)
+                               rt.fl.fl4_src = inet_select_addr(dev_out, 0,
+                                                                RT_SCOPE_LINK);
                        goto make_route;
                }
-               if (!fl.fl4_src) {
+               if (!rt.fl.fl4_src) {
                        if (MULTICAST(oldflp->fl4_dst))
-                               fl.fl4_src = inet_select_addr(dev_out, 0,
-                                                             fl.fl4_scope);
+                               rt.fl.fl4_src = inet_select_addr(dev_out, 0,
+                                                                
rt.fl.fl4_scope);
                        else if (!oldflp->fl4_dst)
-                               fl.fl4_src = inet_select_addr(dev_out, 0,
-                                                             RT_SCOPE_HOST);
+                               rt.fl.fl4_src = inet_select_addr(dev_out, 0,
+                                                                RT_SCOPE_HOST);
                }
        }
 
-       if (!fl.fl4_dst) {
-               fl.fl4_dst = fl.fl4_src;
-               if (!fl.fl4_dst)
-                       fl.fl4_dst = fl.fl4_src = htonl(INADDR_LOOPBACK);
+       if (!rt.fl.fl4_dst) {
+               rt.fl.fl4_dst = rt.fl.fl4_src;
+               if (!rt.fl.fl4_dst)
+                       rt.fl.fl4_dst = rt.fl.fl4_src = htonl(INADDR_LOOPBACK);
                if (dev_out)
                        dev_put(dev_out);
                dev_out = net->loopback_dev;
                dev_hold(dev_out);
-               fl.oif = net->loopback_dev->ifindex;
+               rt.fl.oif = net->loopback_dev->ifindex;
                res.type = RTN_LOCAL;
                flags |= RTCF_LOCAL;
                goto make_route;
        }
 
-       if (fib_lookup(&fl, &res)) {
+       if (fib_lookup(&rt.fl, &res)) {
                res.fi = NULL;
                if (oldflp->oif) {
                        /* Apparently, routing tables are wrong. Assume,
@@ -2306,9 +2311,9 @@ static int ip_route_output_slow(struct r
                           likely IPv6, but we do not.
                         */
 
-                       if (fl.fl4_src == 0)
-                               fl.fl4_src = inet_select_addr(dev_out, 0,
-                                                             RT_SCOPE_LINK);
+                       if (rt.fl.fl4_src == 0)
+                               rt.fl.fl4_src = inet_select_addr(dev_out, 0,
+                                                                RT_SCOPE_LINK);
                        res.type = RTN_UNICAST;
                        goto make_route;
                }
@@ -2320,13 +2325,13 @@ static int ip_route_output_slow(struct r
        free_res = 1;
 
        if (res.type == RTN_LOCAL) {
-               if (!fl.fl4_src)
-                       fl.fl4_src = fl.fl4_dst;
+               if (!rt.fl.fl4_src)
+                       rt.fl.fl4_src = rt.fl.fl4_dst;
                if (dev_out)
                        dev_put(dev_out);
                dev_out = net->loopback_dev;
                dev_hold(dev_out);
-               fl.oif = dev_out->ifindex;
+               rt.fl.oif = dev_out->ifindex;
                if (res.fi)
                        fib_info_put(res.fi);
                res.fi = NULL;
@@ -2336,24 +2341,24 @@ static int ip_route_output_slow(struct r
 
 #ifdef CONFIG_IP_ROUTE_MULTIPATH
        if (res.fi->fib_nhs > 1 && fl.oif == 0)
-               fib_select_multipath(&fl, &res);
+               fib_select_multipath(&rt.fl, &res);
        else
 #endif
-       if (!res.prefixlen && res.type == RTN_UNICAST && !fl.oif)
-               fib_select_default(&fl, &res);
+       if (!res.prefixlen && res.type == RTN_UNICAST && !rt.fl.oif)
+               fib_select_default(&rt.fl, &res);
 
-       if (!fl.fl4_src)
-               fl.fl4_src = FIB_RES_PREFSRC(res);
+       if (!rt.fl.fl4_src)
+               rt.fl.fl4_src = FIB_RES_PREFSRC(res);
 
        if (dev_out)
                dev_put(dev_out);
        dev_out = FIB_RES_DEV(res);
        dev_hold(dev_out);
-       fl.oif = dev_out->ifindex;
+       rt.fl.oif = dev_out->ifindex;
 
 
 make_route:
-       err = ip_mkroute_output(rp, &res, &fl, oldflp, dev_out, flags);
+       err = ip_mkroute_output(rp, &res, &rt.fl, oldflp, dev_out, flags);
 
 
        if (free_res)
Index: linux-2.6-netns/include/net/ip_fib.h
===================================================================
--- linux-2.6-netns.orig/include/net/ip_fib.h
+++ linux-2.6-netns/include/net/ip_fib.h
@@ -173,7 +173,8 @@ static inline struct fib_table *fib_new_
 
 static inline int fib_lookup(const struct flowi *flp, struct fib_result *res)
 {
-       struct net *net = flp->fl_net;
+       struct rtable *rt = container_of(flp, struct rtable, fl);
+       struct net *net = rt->u.dst.net;
        struct fib_table *local_table = net->ip_fib_local_table;
        struct fib_table *main_table = net->ip_fib_main_table;
        if (local_table->tb_lookup(local_table, flp, res) &&

-- 
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