IPv6 routing, NLM_F_* flag support: REPLACE and EXCL flags support, warn about missing CREATE flag

The support for NLM_F_* flags at IPv6 routing requests.

If NLM_F_CREATE flag is not defined for RTM_NEWROUTE request,
warning is printed, but no error is returned. Instead new route is
added. Later NLM_F_CREATE may be required for
new route creation.

Exception is when NLM_F_REPLACE flag is given without NLM_F_CREATE, and
no matching route is found. In this case it should be safe to assume
that the request issuer is familiar with NLM_F_* flags, and does really
not want route to be created.

Specifying NLM_F_REPLACE flag will now make the kernel to search for
matching route, and replace it with new one. If no route is found and
NLM_F_CREATE is specified as well, then new route is created.

Also, specifying NLM_F_EXCL will yield returning of error if matching
route is found.

Patch created against linux-3.2-rc1

Signed-off-by: Matti Vaittinen <Mazziesaccount@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 94 insertions, 15 deletions

diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c
index 93718f3db79b..9239d559b41b 100644
--- a/net/ipv6/ip6_fib.c
+++ b/net/ipv6/ip6_fib.c
@@ -425,7 +425,8 @@ out:
 
 static struct fib6_node * fib6_add_1(struct fib6_node *root, void *addr,
                                      int addrlen, int plen,
-                                     int offset)
+                                     int offset, int allow_create,
+                                     int replace_required)
 {
         struct fib6_node *fn, *in, *ln;
         struct fib6_node *pn = NULL;
@@ -447,8 +448,12 @@ static struct fib6_node * fib6_add_1(struct fib6_node *root, void *addr,
                  *      Prefix match
                  */
                 if (plen < fn->fn_bit ||
-                    !ipv6_prefix_equal(&key->addr, addr, fn->fn_bit))
+                    !ipv6_prefix_equal(&key->addr, addr, fn->fn_bit)) {
+                        if (!allow_create)
+                                printk(KERN_WARNING
+                                    "IPv6: NLM_F_CREATE should be set when creating new route\n");
                         goto insert_above;
+                }
 
                 /*
                  *      Exact match ?
@@ -477,10 +482,26 @@ static struct fib6_node * fib6_add_1(struct fib6_node *root, void *addr,
                 fn = dir ? fn->right: fn->left;
         } while (fn);
 
+        if (replace_required && !allow_create) {
+                /* We should not create new node because
+                 * NLM_F_REPLACE was specified without NLM_F_CREATE
+                 * I assume it is safe to require NLM_F_CREATE when
+                 * REPLACE flag is used! Later we may want to remove the
+                 * check for replace_required, because according
+                 * to netlink specification, NLM_F_CREATE
+                 * MUST be specified if new route is created.
+                 * That would keep IPv6 consistent with IPv4
+                 */
+                printk(KERN_WARNING
+                    "IPv6: NLM_F_CREATE should be set when creating new route - ignoring request\n");
+                return ERR_PTR(-ENOENT);
+        }
         /*
          *      We walked to the bottom of tree.
          *      Create new leaf node without children.
          */
+        if (!allow_create)
+                printk(KERN_WARNING "IPv6: NLM_F_CREATE should be set when creating new route\n");
 
         ln = node_alloc();
 
@@ -614,6 +635,12 @@ static int fib6_add_rt2node(struct fib6_node *fn, struct rt6_info *rt,
 {
         struct rt6_info *iter = NULL;
         struct rt6_info **ins;
+        int replace = (NULL != info &&
+            NULL != info->nlh &&
+            (info->nlh->nlmsg_flags&NLM_F_REPLACE));
+        int add = ((NULL == info || NULL == info->nlh) ||
+            (info->nlh->nlmsg_flags&NLM_F_CREATE));
+        int found = 0;
 
         ins = &fn->leaf;
 
@@ -626,6 +653,13 @@ static int fib6_add_rt2node(struct fib6_node *fn, struct rt6_info *rt,
                         /*
                          *      Same priority level
                          */
+                        if (NULL != info->nlh &&
+                            (info->nlh->nlmsg_flags&NLM_F_EXCL))
+                                return -EEXIST;
+                        if (replace) {
+                                found++;
+                                break;
+                        }
 
                         if (iter->rt6i_dev == rt->rt6i_dev &&
                             iter->rt6i_idev == rt->rt6i_idev &&
@@ -655,17 +689,40 @@ static int fib6_add_rt2node(struct fib6_node *fn, struct rt6_info *rt,
         /*
          *      insert node
          */
+        if (!replace) {
+                if (!add)
+                        printk(KERN_WARNING "IPv6: NLM_F_CREATE should be set when creating new route\n");
+
+add:
+                rt->dst.rt6_next = iter;
+                *ins = rt;
+                rt->rt6i_node = fn;
+                atomic_inc(&rt->rt6i_ref);
+                inet6_rt_notify(RTM_NEWROUTE, rt, info);
+                info->nl_net->ipv6.rt6_stats->fib_rt_entries++;
+
+                if ((fn->fn_flags & RTN_RTINFO) == 0) {
+                        info->nl_net->ipv6.rt6_stats->fib_route_nodes++;
+                        fn->fn_flags |= RTN_RTINFO;
+                }
 
-        rt->dst.rt6_next = iter;
-        *ins = rt;
-        rt->rt6i_node = fn;
-        atomic_inc(&rt->rt6i_ref);
-        inet6_rt_notify(RTM_NEWROUTE, rt, info);
-        info->nl_net->ipv6.rt6_stats->fib_rt_entries++;
-
-        if ((fn->fn_flags & RTN_RTINFO) == 0) {
-                info->nl_net->ipv6.rt6_stats->fib_route_nodes++;
-                fn->fn_flags |= RTN_RTINFO;
+        } else {
+                if (!found) {
+                        if (add)
+                                goto add;
+                        printk(KERN_WARNING "IPv6: NLM_F_REPLACE set, but no existing node found!\n");
+                        return -ENOENT;
+                }
+                *ins = rt;
+                rt->rt6i_node = fn;
+                rt->dst.rt6_next = iter->dst.rt6_next;
+                atomic_inc(&rt->rt6i_ref);
+                inet6_rt_notify(RTM_NEWROUTE, rt, info);
+                rt6_release(iter);
+                if ((fn->fn_flags & RTN_RTINFO) == 0) {
+                        info->nl_net->ipv6.rt6_stats->fib_route_nodes++;
+                        fn->fn_flags |= RTN_RTINFO;
+                }
         }
 
         return 0;
@@ -696,9 +753,25 @@ int fib6_add(struct fib6_node *root, struct rt6_info *rt, struct nl_info *info)
 {
         struct fib6_node *fn, *pn = NULL;
         int err = -ENOMEM;
+        int allow_create = 1;
+        int replace_required = 0;
+        if (NULL != info && NULL != info->nlh) {
+                if (!(info->nlh->nlmsg_flags&NLM_F_CREATE))
+                        allow_create = 0;
+                if ((info->nlh->nlmsg_flags&NLM_F_REPLACE))
+                        replace_required = 1;
+        }
+        if (!allow_create && !replace_required)
+                printk(KERN_WARNING "IPv6: RTM_NEWROUTE with no NLM_F_CREATE or NLM_F_REPLACE\n");
 
         fn = fib6_add_1(root, &rt->rt6i_dst.addr, sizeof(struct in6_addr),
-                        rt->rt6i_dst.plen, offsetof(struct rt6_info, rt6i_dst));
+                    rt->rt6i_dst.plen, offsetof(struct rt6_info, rt6i_dst),
+                    allow_create, replace_required);
+
+        if (IS_ERR(fn)) {
+                err = PTR_ERR(fn);
+                fn = NULL;
+        }
 
         if (fn == NULL)
                 goto out;
@@ -736,7 +809,8 @@ int fib6_add(struct fib6_node *root, struct rt6_info *rt, struct nl_info *info)
 
                         sn = fib6_add_1(sfn, &rt->rt6i_src.addr,
                                         sizeof(struct in6_addr), rt->rt6i_src.plen,
-                                        offsetof(struct rt6_info, rt6i_src));
+                                        offsetof(struct rt6_info, rt6i_src),
+                                        allow_create, replace_required);
 
                         if (sn == NULL) {
                                 /* If it is failed, discard just allocated
@@ -753,8 +827,13 @@ int fib6_add(struct fib6_node *root, struct rt6_info *rt, struct nl_info *info)
                 } else {
                         sn = fib6_add_1(fn->subtree, &rt->rt6i_src.addr,
                                         sizeof(struct in6_addr), rt->rt6i_src.plen,
-                                        offsetof(struct rt6_info, rt6i_src));
+                                        offsetof(struct rt6_info, rt6i_src),
+                                        allow_create, replace_required);
 
+                        if (IS_ERR(sn)) {
+                                err = PTR_ERR(sn);
+                                sn = NULL;
+                        }
                         if (sn == NULL)
                                 goto st_failure;
                 }