[PATCH libnftnl 2/2] utils: add NFCT_FILTER_DUMP_TUPLE example

[Romain Bellan <romain.bellan@wifirst.fr>]

Simple example to see conntrack kernel side filtering configuration.
Callback is reading the kernel result, and user is notified when kernel
does not support filtering (so filtering must be done in userspace)

Signed-off-by: Romain Bellan <romain.bellan@wifirst.fr>
Signed-off-by: Florent Fourcot <florent.fourcot@wifirst.fr>
---
 utils/.gitignore                    |  1 +
 utils/Makefile.am                   |  4 ++
 utils/conntrack_dump_filter_tuple.c | 70 +++++++++++++++++++++++++++++
 3 files changed, 75 insertions(+)
 create mode 100644 utils/conntrack_dump_filter_tuple.c

diff --git a/utils/.gitignore b/utils/.gitignore
index 63dfcb2..0de05c0 100644
--- a/utils/.gitignore
+++ b/utils/.gitignore
@@ -3,6 +3,7 @@
 /conntrack_delete
 /conntrack_dump
 /conntrack_dump_filter
+/conntrack_dump_filter_tuple
 /conntrack_events
 /conntrack_filter
 /conntrack_flush
diff --git a/utils/Makefile.am b/utils/Makefile.am
index 69bafe6..438ca74 100644
--- a/utils/Makefile.am
+++ b/utils/Makefile.am
@@ -9,6 +9,7 @@ check_PROGRAMS = expect_dump expect_create expect_get expect_delete \
 	       conntrack_master conntrack_filter \
 	       conntrack_grp_create \
 	       conntrack_dump_filter \
+	       conntrack_dump_filter_tuple \
 	       ctexp_events
 
 conntrack_grp_create_SOURCES = conntrack_grp_create.c
@@ -35,6 +36,9 @@ conntrack_dump_LDADD = ../src/libnetfilter_conntrack.la
 conntrack_dump_filter_SOURCES = conntrack_dump_filter.c
 conntrack_dump_filter_LDADD = ../src/libnetfilter_conntrack.la
 
+conntrack_dump_filter_tuple_SOURCES = conntrack_dump_filter_tuple.c
+conntrack_dump_filter_tuple_LDADD = ../src/libnetfilter_conntrack.la
+
 conntrack_flush_SOURCES = conntrack_flush.c
 conntrack_flush_LDADD = ../src/libnetfilter_conntrack.la
 
diff --git a/utils/conntrack_dump_filter_tuple.c b/utils/conntrack_dump_filter_tuple.c
new file mode 100644
index 0000000..44633da
--- /dev/null
+++ b/utils/conntrack_dump_filter_tuple.c
@@ -0,0 +1,70 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <arpa/inet.h>
+
+#include <libnetfilter_conntrack/libnetfilter_conntrack.h>
+
+static int cb(const struct nlmsghdr *nlh,
+	      enum nf_conntrack_msg_type type,
+	      struct nf_conntrack *ct,
+	      void *data)
+{
+	char buf[1024];
+
+	if (!(nlh->nlmsg_flags & NLM_F_DUMP_FILTERED))
+	  {
+	    fprintf(stderr, "No filtering in kernel, do filtering in userspace\n");
+	    return NFCT_CB_FAILURE;
+	  }
+
+	nfct_snprintf(buf, sizeof(buf), ct, NFCT_T_UNKNOWN, NFCT_O_DEFAULT, NFCT_OF_SHOW_LAYER3 | NFCT_OF_TIMESTAMP);
+	printf("%s\n", buf);
+
+	return NFCT_CB_CONTINUE;
+}
+
+int main(void)
+{
+	int ret;
+	struct nfct_handle *h;
+
+	h = nfct_open(CONNTRACK, 0);
+	if (!h) {
+		perror("nfct_open");
+		return -1;
+	}
+	struct nfct_filter_dump *filter_dump = nfct_filter_dump_create();
+	if (filter_dump == NULL) {
+		perror("nfct_filter_dump_alloc");
+		return -1;
+	}
+
+	struct nf_conntrack	*ct;
+	ct = nfct_new();
+	if (!ct) {
+		perror("nfct_new");
+		return 0;
+	}
+
+	nfct_set_attr_u8(ct, ATTR_ORIG_L3PROTO, AF_INET);
+	nfct_set_attr_u8(ct, ATTR_L4PROTO, IPPROTO_ICMP);
+	nfct_set_attr_u32(ct, ATTR_ORIG_IPV4_DST, inet_addr("203.0.113.55"));
+	nfct_filter_dump_set_attr(filter_dump, NFCT_FILTER_DUMP_TUPLE, ct);
+
+	nfct_callback_register2(h, NFCT_T_ALL, cb, NULL);
+	ret = nfct_query(h, NFCT_Q_DUMP_FILTER, filter_dump);
+
+	nfct_filter_dump_destroy(filter_dump);
+
+	printf("TEST: get conntrack ");
+	if (ret == -1)
+		printf("(%d)(%s)\n", ret, strerror(errno));
+	else
+		printf("(OK)\n");
+
+	nfct_close(h);
+
+	ret == -1 ? exit(EXIT_FAILURE) : exit(EXIT_SUCCESS);
+}
-- 
2.20.1