ldpd: add synchronous IPC channels

By default all ldpd interprocess communication is asynchronous
(non-blocking socketpairs). Under some circumstances, however, we'll
need synchronous IPC as well. Examples:
* the lde child process requesting labels to zebra (through the parent
  process);
* apply an access-list on a given IP prefix (ACLs are only available in
  the parent process).

This patch only adds the necessary infrastructure to allow the child
processes to make synchronous requests to the parent process. Later
patches will make use of this new infrastructure.

Signed-off-by: Renato Westphal <renato@opensourcerouting.org>

4 files changed, 72 insertions, 29 deletions

diff --git a/ldpd/lde.c b/ldpd/lde.c
index 91b2b1727..a28862881 100644
--- a/ldpd/lde.c
+++ b/ldpd/lde.c
@@ -58,7 +58,7 @@ struct ldpd_conf	*ldeconf;
 struct nbr_tree		 lde_nbrs = RB_INITIALIZER(&lde_nbrs);
 
 static struct imsgev	*iev_ldpe;
-static struct imsgev	*iev_main;
+static struct imsgev	*iev_main, *iev_main_sync;
 
 /* Master of threads. */
 struct thread_master *master;
@@ -133,15 +133,18 @@ lde(const char *user, const char *group)
 	/* setup signal handler */
 	signal_init(master, array_size(lde_signals), lde_signals);
 
-	/* setup pipe and event handler to the parent process */
-	if ((iev_main = malloc(sizeof(struct imsgev))) == NULL)
+	/* setup pipes and event handlers to the parent process */
+	if ((iev_main = calloc(1, sizeof(struct imsgev))) == NULL)
 		fatal(NULL);
-	imsg_init(&iev_main->ibuf, 3);
+	imsg_init(&iev_main->ibuf, LDPD_FD_ASYNC);
 	iev_main->handler_read = lde_dispatch_parent;
 	iev_main->ev_read = thread_add_read(master, iev_main->handler_read,
 	    iev_main, iev_main->ibuf.fd);
 	iev_main->handler_write = ldp_write_handler;
-	iev_main->ev_write = NULL;
+
+	if ((iev_main_sync = calloc(1, sizeof(struct imsgev))) == NULL)
+		fatal(NULL);
+	imsg_init(&iev_main_sync->ibuf, LDPD_FD_SYNC);
 
 	/* start the LIB garbage collector */
 	lde_gc_start_timer();
@@ -162,6 +165,8 @@ lde_shutdown(void)
 	close(iev_ldpe->ibuf.fd);
 	msgbuf_clear(&iev_main->ibuf.w);
 	close(iev_main->ibuf.fd);
+	msgbuf_clear(&iev_main_sync->ibuf.w);
+	close(iev_main_sync->ibuf.fd);
 
 	lde_gc_stop_timer();
 	lde_nbr_clear();
@@ -171,6 +176,7 @@ lde_shutdown(void)
 
 	free(iev_ldpe);
 	free(iev_main);
+	free(iev_main_sync);
 
 	log_info("label decision engine exiting");
 	exit(0);
diff --git a/ldpd/ldpd.c b/ldpd/ldpd.c
index c9f4e37ee..6fd4251ed 100644
--- a/ldpd/ldpd.c
+++ b/ldpd/ldpd.c
@@ -42,7 +42,7 @@
 #include "qobj.h"
 
 static void		 ldpd_shutdown(void);
-static pid_t		 start_child(enum ldpd_process, char *, int,
+static pid_t		 start_child(enum ldpd_process, char *, int, int,
 			    const char *, const char *);
 static int		 main_dispatch_ldpe(struct thread *);
 static int		 main_dispatch_lde(struct thread *);
@@ -77,8 +77,8 @@ DEFINE_QOBJ_TYPE(ldpd_conf)
 struct ldpd_global	 global;
 struct ldpd_conf	*ldpd_conf;
 
-static struct imsgev	*iev_ldpe;
-static struct imsgev	*iev_lde;
+static struct imsgev	*iev_ldpe, *iev_ldpe_sync;
+static struct imsgev	*iev_lde, *iev_lde_sync;
 static pid_t		 ldpe_pid;
 static pid_t		 lde_pid;
 
@@ -207,8 +207,8 @@ main(int argc, char *argv[])
 {
 	char			*saved_argv0;
 	int			 lflag = 0, eflag = 0;
-	int			 pipe_parent2ldpe[2];
-	int			 pipe_parent2lde[2];
+	int			 pipe_parent2ldpe[2], pipe_parent2ldpe_sync[2];
+	int			 pipe_parent2lde[2], pipe_parent2lde_sync[2];
 	char			*p;
 	char			*vty_addr = NULL;
 	int			 vty_port = LDP_VTY_PORT;
@@ -347,22 +347,34 @@ main(int argc, char *argv[])
 
 	if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, pipe_parent2ldpe) == -1)
 		fatal("socketpair");
+	if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC,
+	    pipe_parent2ldpe_sync) == -1)
+		fatal("socketpair");
 	if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, pipe_parent2lde) == -1)
 		fatal("socketpair");
+	if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC,
+	    pipe_parent2lde_sync) == -1)
+		fatal("socketpair");
 	sock_set_nonblock(pipe_parent2ldpe[0]);
 	sock_set_cloexec(pipe_parent2ldpe[0]);
 	sock_set_nonblock(pipe_parent2ldpe[1]);
 	sock_set_cloexec(pipe_parent2ldpe[1]);
+	sock_set_nonblock(pipe_parent2ldpe_sync[0]);
+	sock_set_cloexec(pipe_parent2ldpe_sync[0]);
+	sock_set_cloexec(pipe_parent2ldpe_sync[1]);
 	sock_set_nonblock(pipe_parent2lde[0]);
 	sock_set_cloexec(pipe_parent2lde[0]);
 	sock_set_nonblock(pipe_parent2lde[1]);
 	sock_set_cloexec(pipe_parent2lde[1]);
+	sock_set_nonblock(pipe_parent2lde_sync[0]);
+	sock_set_cloexec(pipe_parent2lde_sync[0]);
+	sock_set_cloexec(pipe_parent2lde_sync[1]);
 
 	/* start children */
 	lde_pid = start_child(PROC_LDE_ENGINE, saved_argv0,
-	    pipe_parent2lde[1], user, group);
+	    pipe_parent2lde[1], pipe_parent2lde_sync[1], user, group);
 	ldpe_pid = start_child(PROC_LDP_ENGINE, saved_argv0,
-	    pipe_parent2ldpe[1], user, group);
+	    pipe_parent2ldpe[1], pipe_parent2ldpe_sync[1], user, group);
 
 	/* drop privileges */
 	if (user)
@@ -378,22 +390,34 @@ main(int argc, char *argv[])
 	ldp_zebra_init(master);
 
 	/* setup pipes to children */
-	if ((iev_ldpe = malloc(sizeof(struct imsgev))) == NULL ||
-	    (iev_lde = malloc(sizeof(struct imsgev))) == NULL)
+	if ((iev_ldpe = calloc(1, sizeof(struct imsgev))) == NULL ||
+	    (iev_ldpe_sync = calloc(1, sizeof(struct imsgev))) == NULL ||
+	    (iev_lde = calloc(1, sizeof(struct imsgev))) == NULL ||
+	    (iev_lde_sync = calloc(1, sizeof(struct imsgev))) == NULL)
 		fatal(NULL);
 	imsg_init(&iev_ldpe->ibuf, pipe_parent2ldpe[0]);
 	iev_ldpe->handler_read = main_dispatch_ldpe;
 	iev_ldpe->ev_read = thread_add_read(master, iev_ldpe->handler_read,
 	    iev_ldpe, iev_ldpe->ibuf.fd);
 	iev_ldpe->handler_write = ldp_write_handler;
-	iev_ldpe->ev_write = NULL;
+
+	imsg_init(&iev_ldpe_sync->ibuf, pipe_parent2ldpe_sync[0]);
+	iev_ldpe_sync->handler_read = main_dispatch_ldpe;
+	iev_ldpe_sync->ev_read = thread_add_read(master,
+	    iev_ldpe_sync->handler_read, iev_ldpe_sync, iev_ldpe_sync->ibuf.fd);
+	iev_ldpe_sync->handler_write = ldp_write_handler;
 
 	imsg_init(&iev_lde->ibuf, pipe_parent2lde[0]);
 	iev_lde->handler_read = main_dispatch_lde;
 	iev_lde->ev_read = thread_add_read(master, iev_lde->handler_read,
 	    iev_lde, iev_lde->ibuf.fd);
 	iev_lde->handler_write = ldp_write_handler;
-	iev_lde->ev_write = NULL;
+
+	imsg_init(&iev_lde_sync->ibuf, pipe_parent2lde_sync[0]);
+	iev_lde_sync->handler_read = main_dispatch_lde;
+	iev_lde_sync->ev_read = thread_add_read(master,
+	    iev_lde_sync->handler_read, iev_lde_sync, iev_lde_sync->ibuf.fd);
+	iev_lde_sync->handler_write = ldp_write_handler;
 
 	if (main_imsg_send_ipc_sockets(&iev_ldpe->ibuf, &iev_lde->ibuf))
 		fatal("could not establish imsg links");
@@ -466,8 +490,8 @@ ldpd_shutdown(void)
 }
 
 static pid_t
-start_child(enum ldpd_process p, char *argv0, int fd, const char *user,
-    const char *group)
+start_child(enum ldpd_process p, char *argv0, int fd_async, int fd_sync,
+    const char *user, const char *group)
 {
 	char	*argv[7];
 	int	 argc = 0;
@@ -479,12 +503,15 @@ start_child(enum ldpd_process p, char *argv0, int fd, const char *user,
 	case 0:
 		break;
 	default:
-		close(fd);
+		close(fd_async);
+		close(fd_sync);
 		return (pid);
 	}
 
-	if (dup2(fd, 3) == -1)
-		fatal("cannot setup imsg fd");
+	if (dup2(fd_async, LDPD_FD_ASYNC) == -1)
+		fatal("cannot setup imsg async fd");
+	if (dup2(fd_sync, LDPD_FD_SYNC) == -1)
+		fatal("cannot setup imsg sync fd");
 
 	argv[argc++] = argv0;
 	switch (p) {
@@ -702,10 +729,11 @@ main_imsg_compose_both(enum imsg_type type, void *buf, uint16_t len)
 void
 imsg_event_add(struct imsgev *iev)
 {
-	THREAD_READ_ON(master, iev->ev_read, iev->handler_read, iev,
-	    iev->ibuf.fd);
+	if (iev->handler_read)
+		THREAD_READ_ON(master, iev->ev_read, iev->handler_read, iev,
+		    iev->ibuf.fd);
 
-	if (iev->ibuf.w.queued)
+	if (iev->handler_write && iev->ibuf.w.queued)
 		THREAD_WRITE_ON(master, iev->ev_write, iev->handler_write, iev,
 		    iev->ibuf.fd);
 }
diff --git a/ldpd/ldpd.h b/ldpd/ldpd.h
index 3f6d7ac56..2c9706cf4 100644
--- a/ldpd/ldpd.h
+++ b/ldpd/ldpd.h
@@ -33,6 +33,9 @@
 #define CONF_FILE		"/etc/ldpd.conf"
 #define LDPD_USER		"_ldpd"
 
+#define LDPD_FD_ASYNC		3
+#define LDPD_FD_SYNC		4
+
 #define LDPD_OPT_VERBOSE	0x00000001
 #define LDPD_OPT_VERBOSE2	0x00000002
 #define LDPD_OPT_NOACTION	0x00000004
diff --git a/ldpd/ldpe.c b/ldpd/ldpe.c
index 1a60af8f4..236e71f32 100644
--- a/ldpd/ldpe.c
+++ b/ldpd/ldpe.c
@@ -48,7 +48,7 @@ struct ldpd_conf	*leconf;
 struct ldpd_sysdep	 sysdep;
 #endif
 
-static struct imsgev	*iev_main;
+static struct imsgev	*iev_main, *iev_main_sync;
 static struct imsgev	*iev_lde;
 #ifdef __OpenBSD__
 static struct thread	*pfkey_ev;
@@ -142,15 +142,18 @@ ldpe(const char *user, const char *group)
 	/* setup signal handler */
 	signal_init(master, array_size(ldpe_signals), ldpe_signals);
 
-	/* setup pipe and event handler to the parent process */
-	if ((iev_main = malloc(sizeof(struct imsgev))) == NULL)
+	/* setup pipes and event handlers to the parent process */
+	if ((iev_main = calloc(1, sizeof(struct imsgev))) == NULL)
 		fatal(NULL);
-	imsg_init(&iev_main->ibuf, 3);
+	imsg_init(&iev_main->ibuf, LDPD_FD_ASYNC);
 	iev_main->handler_read = ldpe_dispatch_main;
 	iev_main->ev_read = thread_add_read(master, iev_main->handler_read,
 	    iev_main, iev_main->ibuf.fd);
 	iev_main->handler_write = ldp_write_handler;
-	iev_main->ev_write = NULL;
+
+	if ((iev_main_sync = calloc(1, sizeof(struct imsgev))) == NULL)
+		fatal(NULL);
+	imsg_init(&iev_main_sync->ibuf, LDPD_FD_SYNC);
 
 #ifdef __OpenBSD__
 	if (sysdep.no_pfkey == 0)
@@ -191,6 +194,8 @@ ldpe_shutdown(void)
 	msgbuf_write(&iev_main->ibuf.w);
 	msgbuf_clear(&iev_main->ibuf.w);
 	close(iev_main->ibuf.fd);
+	msgbuf_clear(&iev_main_sync->ibuf.w);
+	close(iev_main_sync->ibuf.fd);
 
 	control_cleanup();
 	config_clear(leconf);
@@ -215,6 +220,7 @@ ldpe_shutdown(void)
 	/* clean up */
 	free(iev_lde);
 	free(iev_main);
+	free(iev_main_sync);
 	free(pkt_ptr);
 
 	log_info("ldp engine exiting");