Implement a send queue for each control fd.

Only one call to write(2) should be performed for each POLLOUT check
via poll(2) so we should never see EAGAIN when writing to control
sockets ever again.
Each fd queue is limited to 100 entries so we don't OOM with badly
written control subscribers.

1 files changed, 8 insertions, 47 deletions

diff --git a/dhcpcd.c b/dhcpcd.c
index 23142094..13ece6a9 100644
--- a/dhcpcd.c
+++ b/dhcpcd.c
@@ -1047,42 +1047,6 @@ signal_init(void (*func)(int, siginfo_t *, void *), sigset_t *oldset)
 #endif
 
 static void
-dhcpcd_version(void *arg)
-{
-	struct fd_list *fd = arg;
-	size_t len;
-	struct iovec iov[2];
-
-	len = strlen(VERSION) + 1;
-	iov[0].iov_base = &len;
-	iov[0].iov_len = sizeof(ssize_t);
-	iov[1].iov_base = UNCONST(VERSION);
-	iov[1].iov_len = len;
-	if (writev(fd->fd, iov, 2) == -1)
-		syslog(LOG_ERR, "%s: writev: %m", __func__);
-	else
-		eloop_event_delete(fd->ctx->eloop, fd->fd, 1);
-}
-
-static void
-dhcpcd_getconfigfile(void *arg)
-{
-	struct fd_list *fd = arg;
-	size_t len;
-	struct iovec iov[2];
-
-	len = strlen(fd->ctx->cffile) + 1;
-	iov[0].iov_base = &len;
-	iov[0].iov_len = sizeof(ssize_t);
-	iov[1].iov_base = UNCONST(fd->ctx->cffile);
-	iov[1].iov_len = len;
-	if (writev(fd->fd, iov, 2) == -1)
-		syslog(LOG_ERR, "%s: writev: %m", __func__);
-	else
-		eloop_event_delete(fd->ctx->eloop, fd->fd, 1);
-}
-
-static void
 dhcpcd_getinterfaces(void *arg)
 {
 	struct fd_list *fd = arg;
@@ -1101,11 +1065,11 @@ dhcpcd_getinterfaces(void *arg)
 	}
 	if (write(fd->fd, &len, sizeof(len)) != sizeof(len))
 		return;
+	eloop_event_delete(fd->ctx->eloop, fd->fd, 1);
 	TAILQ_FOREACH(ifp, fd->ctx->ifaces, next) {
-		if (send_interface(fd->fd, ifp) == -1)
+		if (send_interface(fd, ifp) == -1)
 			syslog(LOG_ERR, "send_interface %d: %m", fd->fd);
 	}
-	eloop_event_delete(fd->ctx->eloop, fd->fd, 1);
 }
 
 int
@@ -1124,13 +1088,11 @@ dhcpcd_handleargs(struct dhcpcd_ctx *ctx, struct fd_list *fd,
 		 * expected reply we should be safely able just to change the
 		 * write callback on the fd */
 		if (strcmp(*argv, "--version") == 0) {
-			eloop_event_add(fd->ctx->eloop, fd->fd, NULL, NULL,
-			    dhcpcd_version, fd);
-			return 0;
+			return control_queue(fd, UNCONST(VERSION),
+			    strlen(VERSION) + 1, 0);
 		} else if (strcmp(*argv, "--getconfigfile") == 0) {
-			eloop_event_add(fd->ctx->eloop, fd->fd, NULL, NULL,
-			    dhcpcd_getconfigfile, fd);
-			return 0;
+			return control_queue(fd, UNCONST(fd->ctx->cffile),
+			    strlen(fd->ctx->cffile) + 1, 0);
 		} else if (strcmp(*argv, "--getinterfaces") == 0) {
 			eloop_event_add(fd->ctx->eloop, fd->fd, NULL, NULL,
 			    dhcpcd_getinterfaces, fd);
@@ -1146,10 +1108,8 @@ dhcpcd_handleargs(struct dhcpcd_ctx *ctx, struct fd_list *fd,
 	for (opt = 0; opt < argc; opt++)
 		len += strlen(argv[opt]) + 1;
 	tmp = malloc(len);
-	if (tmp == NULL) {
-		syslog(LOG_ERR, "%s: %m", __func__);
+	if (tmp == NULL)
 		return -1;
-	}
 	p = tmp;
 	for (opt = 0; opt < argc; opt++) {
 		l = strlen(argv[opt]);
@@ -1256,6 +1216,7 @@ main(int argc, char **argv)
 	ifo = NULL;
 	ctx.cffile = CONFIG;
 	ctx.pid_fd = ctx.control_fd = ctx.link_fd = -1;
+	TAILQ_INIT(&ctx.control_fds);
 #ifdef PLUGIN_DEV
 	ctx.dev_fd = -1;
 #endif