examples: nft-rule-get: selective rule dumping

Improve nft-rule-get example to demonstrate selective rule dumping when
table and / or chain attributes are set in a rule dump request.

Usage is now as follows:

	nft-rule-get <family> [<table> <chain>] [<xml|json>]

Signed-off-by: Josue Alvarez <jalvarez@toulouse.viveris.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/examples/nft-rule-get.c b/examples/nft-rule-get.c
index 54bee73f0f9043e41662ba247f13cc9a096837c9..6a15d56ef9281cf7454717c3fec8b4872706e097 100644 (file)
--- a/examples/nft-rule-get.c
+++ b/examples/nft-rule-get.c
@@ -46,17 +46,43 @@ err:
        return MNL_CB_OK;
 }
 
+static struct nftnl_rule *setup_rule(uint8_t family, const char *table,
+                                    const char *chain, const char *handle)
+{
+       struct nftnl_rule *r;
+       uint64_t handle_num;
+
+       r = nftnl_rule_alloc();
+       if (r == NULL)
+               return NULL;
+
+       if (table != NULL)
+               nftnl_rule_set_str(r, NFTNL_RULE_TABLE, table);
+       if (chain != NULL)
+               nftnl_rule_set_str(r, NFTNL_RULE_CHAIN, chain);
+
+       nftnl_rule_set_u32(r, NFTNL_RULE_FAMILY, family);
+
+       if (handle != NULL) {
+               handle_num = atoll(handle);
+               nftnl_rule_set_u64(r, NFTNL_RULE_POSITION, handle_num);
+       }
+
+       return r;
+}
+
 int main(int argc, char *argv[])
 {
        struct mnl_socket *nl;
        char buf[MNL_SOCKET_BUFFER_SIZE];
        struct nlmsghdr *nlh;
        uint32_t portid, seq, type = NFTNL_OUTPUT_DEFAULT;
-       struct nftnl_rule *t = NULL;
+       const char *table = NULL, *chain = NULL;
+       struct nftnl_rule *r;
        int ret, family;
 
-       if (argc < 2 || argc > 3) {
-               fprintf(stderr, "Usage: %s <family> [xml|json]\n",
+       if (argc < 2 || argc > 5) {
+               fprintf(stderr, "Usage: %s <family> [<table> <chain>] [xml|json]\n",
                        argv[0]);
                exit(EXIT_FAILURE);
        }
@@ -76,24 +102,30 @@ int main(int argc, char *argv[])
                exit(EXIT_FAILURE);
        }
 
-       if (argc == 3) {
-               if (strcmp(argv[2], "xml") == 0)
+       /* [xml|json] specified */
+       if (argc == 3 || argc == 5) {
+               if (strcmp(argv[argc - 1], "xml") == 0)
                        type = NFTNL_OUTPUT_XML;
-               else if (strcmp(argv[2], "json") == 0)
+               else if (strcmp(argv[argc - 1], "json") == 0)
                        type = NFTNL_OUTPUT_JSON;
        }
 
-       /* XXX requires table, chain and handle attributes for selective get */
-
-       t = nftnl_rule_alloc();
-       if (t == NULL) {
-               perror("OOM");
-               exit(EXIT_FAILURE);
+       /* at least [<table> <chain>] specified */
+       if (argc >= 4) {
+               table = argv[2];
+               chain = argv[3];
        }
 
        seq = time(NULL);
        nlh = nftnl_rule_nlmsg_build_hdr(buf, NFT_MSG_GETRULE, family,
-                                       NLM_F_DUMP, seq);
+                                        NLM_F_DUMP, seq);
+
+       r = setup_rule(family, table, chain, NULL);
+       if (!r) {
+               perror("setup_rule");
+               exit(EXIT_FAILURE);
+       }
+       nftnl_rule_nlmsg_build_payload(nlh, r);
 
        nl = mnl_socket_open(NETLINK_NETFILTER);
        if (nl == NULL) {