mnl: don't send empty set elements netlink message to kernel

The following command:

 # nft --debug=mnl add rule x y flow table xyz { ip saddr timeout 30s counter }

breaks with EINVAL. The following netlink message is causing the
problem:

...
----------------        ------------------
|  0000000044  |        | message length |
| 02572 | R--- |        |  type | flags  |
|  0000000004  |        | sequence number|
|  0000000000  |        |     port ID    |
----------------        ------------------
| 02 00 00 00  |        |  extra header  |
|00008|--|00002|        |len |flags| type|
| 78 79 7a 00  |        |      data      |       x y z
|00008|--|00004|        |len |flags| type|
| 00 00 00 01  |        |      data      |
|00006|--|00001|        |len |flags| type|
| 78 00 00 00  |        |      data      |       x
----------------        ------------------
...

This is incorrect since this describes no elements at all, so it is
useless.  Add upfront check before iterating over the list of set
elements so the netlink message is not placed in the batch.

This patch also adds a set so flow tables are minimally covered.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/src/mnl.c b/src/mnl.c
index 137ecf0d1e01e6f9273dc70c562f94e0c2ddbb3a..d107015c2743f5e860648d861837278f4f1eeba7 100644 (file)
--- a/src/mnl.c
+++ b/src/mnl.c
@@ -825,19 +825,21 @@ int mnl_nft_setelem_add(struct mnl_socket *nf_sock, struct nftnl_set *nls,
        char buf[NFT_NLMSG_MAXSIZE];
        struct nlmsghdr *nlh;
        struct nftnl_set_elems_iter *iter;
-       int ret, err;
+       int ret, err = 0;
 
        iter = nftnl_set_elems_iter_create(nls);
        if (iter == NULL)
                memory_allocation_error();
 
-       do {
+       while (nftnl_set_elems_iter_cur(iter)) {
                nlh = nftnl_set_elem_nlmsg_build_hdr(buf, NFT_MSG_NEWSETELEM,
                                nftnl_set_get_u32(nls, NFTNL_SET_FAMILY),
                                NLM_F_CREATE | NLM_F_ACK | flags, seq);
                ret = nftnl_set_elems_nlmsg_build_payload_iter(nlh, iter);
                err = nft_mnl_talk(nf_sock, nlh, nlh->nlmsg_len, NULL, NULL);
-       } while (ret > 0 && err >= 0);
+               if (ret <= 0 || err < 0)
+                       break;
+       }
 
        nftnl_set_elems_iter_destroy(iter);
 
@@ -879,13 +881,15 @@ static int mnl_nft_setelem_batch(struct nftnl_set *nls,
        if (iter == NULL)
                memory_allocation_error();
 
-       do {
+       while (nftnl_set_elems_iter_cur(iter)) {
                nlh = nftnl_set_elem_nlmsg_build_hdr(nftnl_batch_buffer(batch),
                                cmd, nftnl_set_get_u32(nls, NFTNL_SET_FAMILY),
                                NLM_F_CREATE | flags, seqnum);
                ret = nftnl_set_elems_nlmsg_build_payload_iter(nlh, iter);
                mnl_nft_batch_continue();
-       } while (ret > 0);
+               if (ret <= 0)
+                       break;
+       }
 
        nftnl_set_elems_iter_destroy(iter);
 

diff --git a/tests/py/ip/flowtable.t b/tests/py/ip/flowtable.t
new file mode 100644 (file)
index 0000000..aea57c3
--- /dev/null
+++ b/tests/py/ip/flowtable.t
@@ -0,0 +1,5 @@
+:input;type filter hook input priority 0
+
+*ip;test-ip;input
+
+flow table xyz { ip saddr timeout 30s counter packets 0 bytes 0};ok

diff --git a/tests/py/ip/flowtable.t.payload b/tests/py/ip/flowtable.t.payload
new file mode 100644 (file)
index 0000000..ffadfd2
--- /dev/null
+++ b/tests/py/ip/flowtable.t.payload
@@ -0,0 +1,7 @@
+# flow table xyz { ip saddr timeout 30s counter packets 0 bytes 0}
+xyz test-ip 31
+xyz test-ip 0
+ip test-ip input 
+  [ payload load 4b @ network header + 12 => reg 1 ]
+  [ dynset update reg_key 1 set xyz timeout 30000ms expr [ counter pkts 0 bytes 0 ] ]
+