Limit the number of concurrent on-verify runs

4 files changed, 23 insertions, 0 deletions

diff --git a/src/fastd.c b/src/fastd.c
index 6512bf7..eff605e 100644
--- a/src/fastd.c
+++ b/src/fastd.c
@@ -534,6 +534,11 @@ static inline void init(int argc, char *argv[]) {
 	VECTOR_ALLOC(ctx.peers, 0);
 	VECTOR_ALLOC(ctx.async_pids, 0);
 
+#ifdef WITH_VERIFY
+	if (sem_init(&ctx.verify_limit, 0, VERIFY_LIMIT))
+		exit_errno("sem_init");
+#endif
+
 	if (pthread_attr_init(&ctx.detached_thread))
 		exit_errno("pthread_attr_init");
 	if (pthread_attr_setdetachstate(&ctx.detached_thread, PTHREAD_CREATE_DETACHED))
diff --git a/src/fastd.h b/src/fastd.h
index 19660db..539dd54 100644
--- a/src/fastd.h
+++ b/src/fastd.h
@@ -43,6 +43,7 @@
 #include <fcntl.h>
 #include <pthread.h>
 #include <poll.h>
+#include <semaphore.h>
 #include <stdarg.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -242,6 +243,9 @@ struct fastd_context {
 
 	uint64_t next_peer_id;			/**< An monotonously increasing ID peers are identified with in some components */
 	VECTOR(fastd_peer_t*) peers;		/**< The currectly active peers */
+#ifdef WITH_VERIFY
+	sem_t verify_limit;			/**< Keeps track of the number of verifier threads */
+#endif
 
 #ifdef USE_EPOLL
 	int epoll_fd;				/**< The file descriptor for the epoll facility */
diff --git a/src/fastd_config.h.in b/src/fastd_config.h.in
index 429e42e..2057be1 100644
--- a/src/fastd_config.h.in
+++ b/src/fastd_config.h.in
@@ -120,6 +120,9 @@
 /** How long a peer stays valid after a successful on-verify run */
 #define VERIFY_VALID_TIME 60	/* 1 minute */
 
+/** Maximum number of concurrent on-verify runs */
+#define VERIFY_LIMIT 32
+
 /** The minimum interval between two handshakes with a peer */
 #define MIN_HANDSHAKE_INTERVAL 15
 
diff --git a/src/verify.c b/src/verify.c
index d875a34..f0dbe55 100644
--- a/src/verify.c
+++ b/src/verify.c
@@ -80,6 +80,9 @@ static void * do_verify_thread(void *p) {
 
 	free(arg);
 
+	if (sem_post(&ctx.verify_limit))
+		exit_errno("sem_post");
+
 	return NULL;
 }
 
@@ -105,6 +108,11 @@ fastd_tristate_t fastd_verify_peer(fastd_peer_t *peer, fastd_socket_t *sock, con
 		return ret ? fastd_tristate_true : fastd_tristate_false;
 	}
 	else {
+		if (sem_trywait(&ctx.verify_limit)) {
+			pr_debug("maximum number of verification processes reached");
+			return fastd_tristate_false;
+		}
+
 		verify_arg_t *arg = calloc(1, sizeof(verify_arg_t) + data_len);
 
 		arg->env = env;
@@ -121,6 +129,9 @@ fastd_tristate_t fastd_verify_peer(fastd_peer_t *peer, fastd_socket_t *sock, con
 		if ((errno = pthread_create(&thread, &ctx.detached_thread, do_verify_thread, arg)) != 0) {
 			pr_error_errno("unable to create verify thread");
 
+			if (sem_post(&ctx.verify_limit))
+				exit_errno("sem_post");
+
 			fastd_shell_env_free(env);
 			free(arg);