[iproute2-next,v2,3/3] ss: add checks for bc filter support

diff --git a/misc/Makefile b/misc/Makefile
index 1debfb1..50dae79 100644
--- a/misc/Makefile
+++ b/misc/Makefile
@@ -1,5 +1,5 @@ 
 # SPDX-License-Identifier: GPL-2.0
-SSOBJ=ss.o ssfilter.tab.o
+SSOBJ=ss.o ssfilter_check.o ssfilter.tab.o
 LNSTATOBJ=lnstat.o lnstat_util.o
 
 TARGETS=ss nstat ifstat rtacct lnstat
diff --git a/misc/ss.c b/misc/ss.c
index b9e6b15..1891e9c 100644
--- a/misc/ss.c
+++ b/misc/ss.c
@@ -29,6 +29,7 @@ 
 #include <limits.h>
 #include <stdarg.h>
 
+#include "ss_util.h"
 #include "utils.h"
 #include "rt_names.h"
 #include "ll_map.h"
@@ -39,8 +40,6 @@ 
 #include "cg_map.h"
 
 #include <linux/tcp.h>
-#include <linux/sock_diag.h>
-#include <linux/inet_diag.h>
 #include <linux/unix_diag.h>
 #include <linux/netdevice.h>	/* for MAX_ADDR_LEN */
 #include <linux/filter.h>
@@ -63,24 +62,10 @@ 
 #define AF_VSOCK PF_VSOCK
 #endif
 
-#define MAGIC_SEQ 123456
 #define BUF_CHUNK (1024 * 1024)	/* Buffer chunk allocation size */
 #define BUF_CHUNKS_MAX 5	/* Maximum number of allocated buffer chunks */
 #define LEN_ALIGN(x) (((x) + 1) & ~1)
 
-#define DIAG_REQUEST(_req, _r)						    \
-	struct {							    \
-		struct nlmsghdr nlh;					    \
-		_r;							    \
-	} _req = {							    \
-		.nlh = {						    \
-			.nlmsg_type = SOCK_DIAG_BY_FAMILY,		    \
-			.nlmsg_flags = NLM_F_ROOT|NLM_F_MATCH|NLM_F_REQUEST,\
-			.nlmsg_seq = MAGIC_SEQ,				    \
-			.nlmsg_len = sizeof(_req),			    \
-		},							    \
-	}
-
 #if HAVE_SELINUX
 #include <selinux/selinux.h>
 #else
diff --git a/misc/ss_util.h b/misc/ss_util.h
new file mode 100644
index 0000000..f7e40bb
--- /dev/null
+++ b/misc/ss_util.h
@@ -0,0 +1,22 @@ 
+#ifndef __SS_UTIL_H__
+#define __SS_UTIL_H__
+
+#include <linux/sock_diag.h>
+#include <linux/inet_diag.h>
+
+#define MAGIC_SEQ 123456
+
+#define DIAG_REQUEST(_req, _r)						    \
+	struct {							    \
+		struct nlmsghdr nlh;					    \
+		_r;							    \
+	} _req = {							    \
+		.nlh = {						    \
+			.nlmsg_type = SOCK_DIAG_BY_FAMILY,		    \
+			.nlmsg_flags = NLM_F_ROOT|NLM_F_MATCH|NLM_F_REQUEST,\
+			.nlmsg_seq = MAGIC_SEQ,				    \
+			.nlmsg_len = sizeof(_req),			    \
+		},							    \
+	}
+
+#endif /* __SS_UTIL_H__ */
diff --git a/misc/ssfilter.h b/misc/ssfilter.h
index d85c084..0be3b1e 100644
--- a/misc/ssfilter.h
+++ b/misc/ssfilter.h
@@ -1,20 +1,24 @@ 
-/* SPDX-License-Identifier: GPL-2.0 */
-#define SSF_DCOND 0
-#define SSF_SCOND 1
-#define SSF_OR	  2
-#define SSF_AND	  3
-#define SSF_NOT	  4
-#define SSF_D_GE  5
-#define SSF_D_LE  6
-#define SSF_S_GE  7
-#define SSF_S_LE  8
-#define SSF_S_AUTO  9
-#define SSF_DEVCOND 10
-#define SSF_MARKMASK 11
-#define SSF_CGROUPCOND 12
-
 #include <stdbool.h>
 
+enum {
+	SSF_DCOND,
+	SSF_SCOND,
+	SSF_OR,
+	SSF_AND,
+	SSF_NOT,
+	SSF_D_GE,
+	SSF_D_LE,
+	SSF_S_GE,
+	SSF_S_LE,
+	SSF_S_AUTO,
+	SSF_DEVCOND,
+	SSF_MARKMASK,
+	SSF_CGROUPCOND,
+	SSF__MAX
+};
+
+bool ssfilter_is_supported(int type);
+
 struct ssfilter
 {
 	int type;
diff --git a/misc/ssfilter.y b/misc/ssfilter.y
index b417579..8e16b44 100644
--- a/misc/ssfilter.y
+++ b/misc/ssfilter.y
@@ -12,7 +12,14 @@  typedef struct ssfilter * ssfilter_t;
 
 static struct ssfilter * alloc_node(int type, void *pred)
 {
-	struct ssfilter *n = malloc(sizeof(*n));
+	struct ssfilter *n;
+
+	if (!ssfilter_is_supported(type)) {
+		fprintf(stderr, "It looks like such filter is not supported! Too old kernel?\n");
+		exit(-1);
+	}
+
+	n = malloc(sizeof(*n));
 	if (n == NULL)
 		abort();
 	n->type = type;
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;
+}