1 files changed, 103 insertions, 0 deletions
diff --git a/misc/ssfilter_check.c b/misc/ssfilter_check.c
new file mode 100644
index 0000000..38c960c
--- /dev/null
+++ b/misc/ssfilter_check.c
@@ -0,0 +1,103 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <errno.h>
+
+#include "libnetlink.h"
+#include "ssfilter.h"
+#include "ss_util.h"
+
+static int dummy_filter(struct nlmsghdr *n, void *arg)
+{
+	/* just stops rtnl_dump_filter() */
+	return -1;
+}
+
+static bool cgroup_filter_check(void)
+{
+	struct sockaddr_nl nladdr = { .nl_family = AF_NETLINK };
+	DIAG_REQUEST(req, struct inet_diag_req_v2 r);
+	struct instr {
+		struct inet_diag_bc_op op;
+		__u64 cgroup_id;
+	} __attribute__((packed));
+	int inslen = sizeof(struct instr);
+	struct instr instr = {
+		{ INET_DIAG_BC_CGROUP_COND, inslen, inslen + 4 },
+		0
+	};
+	struct rtnl_handle rth;
+	struct iovec iov[3];
+	struct msghdr msg;
+	struct rtattr rta;
+	int ret = false;
+	int iovlen = 3;
+
+	if (rtnl_open_byproto(&rth, 0, NETLINK_SOCK_DIAG))
+		return false;
+	rth.dump = MAGIC_SEQ;
+	rth.flags = RTNL_HANDLE_F_SUPPRESS_NLERR;
+
+	memset(&req.r, 0, sizeof(req.r));
+	req.r.sdiag_family = AF_INET;
+	req.r.sdiag_protocol = IPPROTO_TCP;
+	req.nlh.nlmsg_len += RTA_LENGTH(inslen);
+
+	rta.rta_type = INET_DIAG_REQ_BYTECODE;
+	rta.rta_len = RTA_LENGTH(inslen);
+
+	iov[0] = (struct iovec) { &req, sizeof(req) };
+	iov[1] = (struct iovec) { &rta, sizeof(rta) };
+	iov[2] = (struct iovec) { &instr, inslen };
+
+	msg = (struct msghdr) {
+		.msg_name = (void *)&nladdr,
+		.msg_namelen = sizeof(nladdr),
+		.msg_iov = iov,
+		.msg_iovlen = iovlen,
+	};
+
+	if (sendmsg(rth.fd, &msg, 0) < 0)
+		goto out;
+
+	if (rtnl_dump_filter(&rth, dummy_filter, NULL) < 0) {
+		ret = (errno != EINVAL);
+		goto out;
+	}
+
+	ret = true;
+
+out:
+	rtnl_close(&rth);
+
+	return ret;
+}
+
+
+struct filter_check_t {
+	bool (*check)(void);
+	int checked:1,
+	    supported:1;
+};
+
+static struct filter_check_t filter_checks[SSF__MAX] = {
+	[SSF_CGROUPCOND] = { cgroup_filter_check, 0 },
+};
+
+bool ssfilter_is_supported(int type)
+{
+	struct filter_check_t f;
+
+	if (type >= SSF__MAX)
+		return false;
+
+	f = filter_checks[type];
+	if (!f.check)
+		return true;
+
+	if (!f.checked) {
+		f.supported = f.check();
+		f.checked = 1;
+	}
+
+	return f.supported;
+}