conntrack: support flush filtering

flushing already supports filtering on the kernel side for value like
mark, l3num or zone. This patch extends the userspace code to also
support this.

To reduce code duplication the `nfct_filter_dump` struct and associated
logic is reused. Note that filtering by tuple is not supported, since
`CTA_FILTER` is not yet supported on the kernel side for flushing.
Trying to use it returns ENOTSUP.

Signed-off-by: Felix Huettner <felix.huettner@mail.schwarz>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

6 files changed, 78 insertions, 0 deletions

diff --git a/include/internal/prototypes.h b/include/internal/prototypes.h
index 5e935f0..82a3f29 100644
--- a/include/internal/prototypes.h
+++ b/include/internal/prototypes.h
@@ -36,6 +36,7 @@ void __copy_fast(struct nf_conntrack *ct1, const struct nf_conntrack *ct);
 int __setup_netlink_socket_filter(int fd, struct nfct_filter *filter);
 
 int __build_filter_dump(struct nfnlhdr *req, size_t size, const struct nfct_filter_dump *filter_dump);
+int __build_filter_flush(struct nfnlhdr *req, size_t size, const struct nfct_filter_dump *filter_dump);
 
 int nfct_build_tuple(struct nlmsghdr *nlh, const struct __nfct_tuple *t, int type);
 int nfct_parse_tuple(const struct nlattr *attr, struct __nfct_tuple *tuple, int dir, uint32_t *set);
diff --git a/src/conntrack/api.c b/src/conntrack/api.c
index 22965f1..2efb175 100644
--- a/src/conntrack/api.c
+++ b/src/conntrack/api.c
@@ -835,6 +835,8 @@ __build_query_ct(struct nfnl_subsys_handle *ssh,
 		break;
 	case NFCT_Q_FLUSH_FILTER:
 		nfct_fill_hdr(req, IPCTNL_MSG_CT_DELETE, NLM_F_ACK, *family, 1);
+		if (__build_filter_flush(req, size, data) < 0)
+			return -1;
 		break;
 	case NFCT_Q_DUMP:
 		nfct_fill_hdr(req, IPCTNL_MSG_CT_GET, NLM_F_DUMP, *family,
diff --git a/src/conntrack/filter_dump.c b/src/conntrack/filter_dump.c
index 0a19985..fd2d002 100644
--- a/src/conntrack/filter_dump.c
+++ b/src/conntrack/filter_dump.c
@@ -64,3 +64,13 @@ int __build_filter_dump(struct nfnlhdr *req, size_t size,
 {
 	return nfct_nlmsg_build_filter(&req->nlh, filter_dump);
 }
+
+int __build_filter_flush(struct nfnlhdr *req, size_t size,
+			const struct nfct_filter_dump *filter_dump)
+{
+	if (filter_dump->set & (1 << NFCT_FILTER_DUMP_TUPLE)) {
+		errno = ENOTSUP;
+		return -1;
+	}
+	return nfct_nlmsg_build_filter(&req->nlh, filter_dump);
+}
diff --git a/utils/.gitignore b/utils/.gitignore
index 0de05c0..c63fd8b 100644
--- a/utils/.gitignore
+++ b/utils/.gitignore
@@ -7,6 +7,7 @@
 /conntrack_events
 /conntrack_filter
 /conntrack_flush
+/conntrack_flush_filter
 /conntrack_get
 /conntrack_grp_create
 /conntrack_master
diff --git a/utils/Makefile.am b/utils/Makefile.am
index 438ca74..7e7aef4 100644
--- a/utils/Makefile.am
+++ b/utils/Makefile.am
@@ -10,6 +10,7 @@ check_PROGRAMS = expect_dump expect_create expect_get expect_delete \
 	       conntrack_grp_create \
 	       conntrack_dump_filter \
 	       conntrack_dump_filter_tuple \
+	       conntrack_flush_filter \
 	       ctexp_events
 
 conntrack_grp_create_SOURCES = conntrack_grp_create.c
@@ -42,6 +43,9 @@ conntrack_dump_filter_tuple_LDADD = ../src/libnetfilter_conntrack.la
 conntrack_flush_SOURCES = conntrack_flush.c
 conntrack_flush_LDADD = ../src/libnetfilter_conntrack.la
 
+conntrack_flush_filter_SOURCES = conntrack_flush_filter.c
+conntrack_flush_filter_LDADD = ../src/libnetfilter_conntrack.la
+
 conntrack_events_SOURCES = conntrack_events.c
 conntrack_events_LDADD = ../src/libnetfilter_conntrack.la
 
diff --git a/utils/conntrack_flush_filter.c b/utils/conntrack_flush_filter.c
new file mode 100644
index 0000000..6e8d93b
--- /dev/null
+++ b/utils/conntrack_flush_filter.c
@@ -0,0 +1,60 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+
+#include <libnetfilter_conntrack/libnetfilter_conntrack.h>
+
+static int cb(enum nf_conntrack_msg_type type,
+	      struct nf_conntrack *ct,
+	      void *data)
+{
+	char buf[1024];
+
+	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 nfct_filter_dump_mark filter_dump_mark = {
+		.val = 1,
+		.mask = 0xffffffff,
+	};
+	nfct_filter_dump_set_attr(filter_dump, NFCT_FILTER_DUMP_MARK,
+					&filter_dump_mark);
+	nfct_filter_dump_set_attr_u8(filter_dump, NFCT_FILTER_DUMP_L3NUM,
+					AF_INET);
+	nfct_filter_dump_set_attr_u16(filter_dump, NFCT_FILTER_DUMP_ZONE,
+					123);
+
+	nfct_callback_register(h, NFCT_T_ALL, cb, NULL);
+	ret = nfct_query(h, NFCT_Q_FLUSH_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);
+}