netfilter: nf_tables: Implement table adoption support

Allow a new process to take ownership of a previously owned table,
useful mostly for firewall management services restarting or suspending
when idle.

By extending __NFT_TABLE_F_UPDATE, the on/off/on check in
nf_tables_updtable() also covers table adoption, although it is actually
not needed: Table adoption is irreversible because nf_tables_updtable()
rejects attempts to drop NFT_TABLE_F_OWNER so table->nlpid setting can
happen just once within the transaction.

If the transaction commences, table's nlpid and flags fields are already
set and no further action is required. If it aborts, the table returns
to orphaned state.

Signed-off-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Florian Westphal <fw@strlen.de>

diff --git a/include/net/netfilter/nf_tables.h b/include/net/netfilter/nf_tables.h
index 4e1ea18eb5f05f763429ed2f75c0c1c9aee20d44..ac7c94d3648e00d75d23dd1d008512133be5e1e0 100644 (file)
--- a/include/net/netfilter/nf_tables.h
+++ b/include/net/netfilter/nf_tables.h
@@ -1271,6 +1271,12 @@ static inline bool nft_table_has_owner(const struct nft_table *table)
        return table->flags & NFT_TABLE_F_OWNER;
 }
 
+static inline bool nft_table_is_orphan(const struct nft_table *table)
+{
+       return (table->flags & (NFT_TABLE_F_OWNER | NFT_TABLE_F_PERSIST)) ==
+                       NFT_TABLE_F_PERSIST;
+}
+
 static inline bool nft_base_chain_netdev(int family, u32 hooknum)
 {
        return family == NFPROTO_NETDEV ||

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 6a96f0003faa96cc231595cf2f91297eb75453b9..b0e0d039897eee2e3b459752e0130fc78ff60088 100644 (file)
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -1194,8 +1194,10 @@ static void nf_tables_table_disable(struct net *net, struct nft_table *table)
 #define __NFT_TABLE_F_INTERNAL         (NFT_TABLE_F_MASK + 1)
 #define __NFT_TABLE_F_WAS_DORMANT      (__NFT_TABLE_F_INTERNAL << 0)
 #define __NFT_TABLE_F_WAS_AWAKEN       (__NFT_TABLE_F_INTERNAL << 1)
+#define __NFT_TABLE_F_WAS_ORPHAN       (__NFT_TABLE_F_INTERNAL << 2)
 #define __NFT_TABLE_F_UPDATE           (__NFT_TABLE_F_WAS_DORMANT | \
-                                        __NFT_TABLE_F_WAS_AWAKEN)
+                                        __NFT_TABLE_F_WAS_AWAKEN | \
+                                        __NFT_TABLE_F_WAS_ORPHAN)
 
 static int nf_tables_updtable(struct nft_ctx *ctx)
 {
@@ -1215,8 +1217,8 @@ static int nf_tables_updtable(struct nft_ctx *ctx)
 
        if ((nft_table_has_owner(ctx->table) &&
             !(flags & NFT_TABLE_F_OWNER)) ||
-           (!nft_table_has_owner(ctx->table) &&
-            flags & NFT_TABLE_F_OWNER))
+           (flags & NFT_TABLE_F_OWNER &&
+            !nft_table_is_orphan(ctx->table)))
                return -EOPNOTSUPP;
 
        if ((flags ^ ctx->table->flags) & NFT_TABLE_F_PERSIST)
@@ -1248,6 +1250,13 @@ static int nf_tables_updtable(struct nft_ctx *ctx)
                }
        }
 
+       if ((flags & NFT_TABLE_F_OWNER) &&
+           !nft_table_has_owner(ctx->table)) {
+               ctx->table->nlpid = ctx->portid;
+               ctx->table->flags |= NFT_TABLE_F_OWNER |
+                                    __NFT_TABLE_F_WAS_ORPHAN;
+       }
+
        nft_trans_table_update(trans) = true;
        nft_trans_commit_list_add_tail(ctx->net, trans);
 
@@ -10423,6 +10432,10 @@ static int __nf_tables_abort(struct net *net, enum nfnl_abort_action action)
                                } else if (trans->ctx.table->flags & __NFT_TABLE_F_WAS_AWAKEN) {
                                        trans->ctx.table->flags &= ~NFT_TABLE_F_DORMANT;
                                }
+                               if (trans->ctx.table->flags & __NFT_TABLE_F_WAS_ORPHAN) {
+                                       trans->ctx.table->flags &= ~NFT_TABLE_F_OWNER;
+                                       trans->ctx.table->nlpid = 0;
+                               }
                                trans->ctx.table->flags &= ~__NFT_TABLE_F_UPDATE;
                                nft_trans_destroy(trans);
                        } else {