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diff --git a/usr.bin/genl/genl.1 b/usr.bin/genl/genl.1
--- a/usr.bin/genl/genl.1
+++ b/usr.bin/genl/genl.1
@@ -24,23 +24,44 @@
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
-.Dd May 20, 2023
+.Dd Oct 5, 2023
.Dt GENL 1
.Os
.Sh NAME
.Nm genl
-.Nd "generic netlink list"
+.Nd "generic netlink"
.Sh SYNOPSIS
.Nm
+.Pp
+.Nm Cm list
+.Pp
+.Nm Cm monitor Ao family Ac Ao multicast group Ac
.Sh DESCRIPTION
+The
.Nm
-lists all available generic netlink protocols, and presents its details:
+utility is design to provide access to the user to generic netlink
+protocols.
+.Pp
+The following commands are available:
+.Bl -tag -ident
+.It Cm list Po default Pc
+Lists all available generic netlink protocols, and presents its details:
.Bl -tag -width "multicast groups"
.It operations
Id of the operation if any and associated capabilities
.It multicast groups
If of the available multicast group if any and it associated name
.El
+.It Cm monitor Ao family Ac Ao multicast group Ac
+Connect to the
+.Ar family
+protocol and subscribe to the
+.Ar mulicast group
+then print the received messages in a readable format if the protocol is known.
+So far only
+.Qq nlctrl
+is known.
+.El
.Sh SEE ALSO
.Xr genetlink 4 ,
.Xr netlink 4
diff --git a/usr.bin/genl/genl.c b/usr.bin/genl/genl.c
--- a/usr.bin/genl/genl.c
+++ b/usr.bin/genl/genl.c
@@ -27,18 +27,41 @@
#include <sys/param.h>
#include <sys/module.h>
+#include <sys/socket.h>
#include <stdint.h>
#include <stdlib.h>
#include <unistd.h>
#include <err.h>
#include <stdio.h>
+#include <poll.h>
#include <netlink/netlink.h>
#include <netlink/netlink_generic.h>
#include <netlink/netlink_snl.h>
#include <netlink/netlink_snl_generic.h>
+static int monitor_mcast(int argc, char **argv);
+static int list_families(int argc, char **argv);
+static void parser_nlctrl_notify(struct snl_state *ss, struct nlmsghdr *hdr);
+static void parser_fallback(struct snl_state *ss, struct nlmsghdr *hdr);
+
+static struct commands {
+ const char *name;
+ const char *usage;
+ int (*cmd)(int argc, char **argv);
+} cmds[] = {
+ { "monitor", "monitor <family> <multicast group>", monitor_mcast },
+ { "list", "list", list_families },
+};
+
+static struct mcast_parsers {
+ const char *family;
+ void (*parser)(struct snl_state *ss, struct nlmsghdr *hdr);
+} mcast_parsers [] = {
+ { "nlctrl", parser_nlctrl_notify },
+};
+
struct genl_ctrl_op {
uint32_t id;
uint32_t flags;
@@ -131,6 +154,13 @@
mcast_groups->groups[i]->mcast_grp_name);
}
+static void
+usage(void)
+{
+ fprintf(stderr, "Usage: %s\n", getprogname());
+ for (size_t i = 0; i < nitems(cmds); i++)
+ fprintf(stderr, " %s %s\n", getprogname(), cmds[i].usage);
+}
static void
dump_family(struct genl_family *family)
@@ -143,8 +173,87 @@
dump_mcast_groups(&family->mcast_groups);
}
+void
+parser_nlctrl_notify(struct snl_state *ss, struct nlmsghdr *hdr)
+{
+ struct genl_family family = {};
+
+ if (snl_parse_nlmsg(ss, hdr, &genl_family_parser,
+ &family))
+ dump_family(&family);
+}
+
+void
+parser_fallback(struct snl_state *ss __unused, struct nlmsghdr *hdr __unused)
+{
+ printf("New unknown message\n");
+}
+
+int
+monitor_mcast(int argc __unused, char **argv)
+{
+ struct snl_state ss;
+ struct nlmsghdr *hdr;
+ struct _getfamily_attrs attrs;
+ struct pollfd pfd;
+ bool found = false;
+ void (*parser)(struct snl_state *ss, struct nlmsghdr *hdr);
+
+ parser = parser_fallback;
+
+ if (!snl_init(&ss, NETLINK_GENERIC))
+ err(EXIT_FAILURE, "snl_init()");
+
+ if (argc != 2) {
+ usage();
+ return (EXIT_FAILURE);
+ }
+ if (!snl_get_genl_family_info(&ss, argv[0], &attrs))
+ errx(EXIT_FAILURE, "Unknown family '%s'", argv[0]);
+ for (uint32_t i = 0; i < attrs.mcast_groups.num_groups; i++) {
+ if (strcmp(attrs.mcast_groups.groups[i]->mcast_grp_name,
+ argv[1]) == 0) {
+ found = true;
+ if (setsockopt(ss.fd, SOL_NETLINK,
+ NETLINK_ADD_MEMBERSHIP,
+ (void *)&attrs.mcast_groups.groups[i]->mcast_grp_id,
+ sizeof(attrs.mcast_groups.groups[i]->mcast_grp_id))
+ == -1)
+ err(EXIT_FAILURE, "Cannot subscribe to command "
+ "notify");
+ break;
+ }
+ }
+ if (!found)
+ errx(EXIT_FAILURE, "No such multicat group '%s'"
+ " in family '%s'", argv[1], argv[0]);
+ for (size_t i= 0; i < nitems(mcast_parsers); i++) {
+ if (strcmp(mcast_parsers[i].family, argv[0]) == 0) {
+ parser = mcast_parsers[i].parser;
+ break;
+ }
+ }
+ memset(&pfd, 0, sizeof(pfd));
+ pfd.fd = ss.fd;
+ pfd.events = POLLIN | POLLERR;
+ while (true) {
+ pfd.revents = 0;
+ if (poll(&pfd, 1, -1) == -1) {
+ if (errno == EINTR)
+ continue;
+ err(EXIT_FAILURE, "poll()");
+ }
+ hdr = snl_read_message(&ss);
+ if (hdr != NULL && hdr->nlmsg_type != NLMSG_ERROR)
+ parser(&ss, hdr);
+
+ }
+
+ return (EXIT_SUCCESS);
+}
+
int
-main(int argc, char **argv __unused)
+list_families(int argc, char **argv __unused)
{
struct snl_state ss;
struct snl_writer nw;
@@ -152,16 +261,16 @@
struct snl_errmsg_data e = {};
uint32_t seq_id;
- if (argc > 1)
- errx(EXIT_FAILURE, "usage: genl does not accept any argument");
- if (modfind("netlink") == -1)
- err(EXIT_FAILURE, "require netlink module to be loaded");
-
+ if (argc != 0) {
+ usage();
+ return (EXIT_FAILURE);
+ }
if (!snl_init(&ss, NETLINK_GENERIC))
err(EXIT_FAILURE, "snl_init()");
snl_init_writer(&ss, &nw);
- hdr = snl_create_genl_msg_request(&nw, GENL_ID_CTRL, CTRL_CMD_GETFAMILY);
+ hdr = snl_create_genl_msg_request(&nw, GENL_ID_CTRL,
+ CTRL_CMD_GETFAMILY);
if ((hdr = snl_finalize_msg(&nw)) == NULL)
err(EXIT_FAILURE, "snl_finalize_msg");
seq_id = hdr->nlmsg_seq;
@@ -179,3 +288,21 @@
return (EXIT_SUCCESS);
}
+
+int
+main(int argc, char **argv)
+{
+ if (modfind("netlink") == -1)
+ err(EXIT_FAILURE, "require netlink module to be loaded");
+
+ if (argc == 1)
+ return (list_families(0, NULL));
+
+ for (size_t i = 0; i < nitems(cmds); i++) {
+ if (strcmp(argv[1], cmds[i].name) == 0)
+ return (cmds[i].cmd(argc - 2, argv + 2));
+ }
+ usage();
+
+ return (EXIT_FAILURE);
+}

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