Add a write callback to eloop so we know when we can write to the socket.

This seems to be important for our control socket as sometimes, we fail to
write with EAGAIN and dhcpcd should not block on users of this socket.

1 files changed, 76 insertions, 42 deletions

diff --git a/dhcpcd.c b/dhcpcd.c
index b19f22bf..130e3c52 100644
--- a/dhcpcd.c
+++ b/dhcpcd.c
@@ -720,7 +720,7 @@ handle_link(void *arg)
 	ctx = arg;
 	if (if_managelink(ctx) == -1) {
 		syslog(LOG_ERR, "if_managelink: %m");
-		eloop_event_delete(ctx->eloop, ctx->link_fd);
+		eloop_event_delete(ctx->eloop, ctx->link_fd, 0);
 		close(ctx->link_fd);
 		ctx->link_fd = -1;
 	}
@@ -1046,6 +1046,68 @@ 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;
+	struct interface *ifp;
+	size_t len;
+
+	len = 0;
+	TAILQ_FOREACH(ifp, fd->ctx->ifaces, next) {
+		len++;
+		if (D_STATE_RUNNING(ifp))
+			len++;
+		if (D6_STATE_RUNNING(ifp))
+			len++;
+		if (ipv6nd_hasra(ifp))
+			len++;
+	}
+	if (write(fd->fd, &len, sizeof(len)) != sizeof(len))
+		return;
+	TAILQ_FOREACH(ifp, fd->ctx->ifaces, next) {
+		if (send_interface(fd->fd, ifp) == -1)
+			syslog(LOG_ERR, "send_interface %d: %m", fd->fd);
+	}
+	eloop_event_delete(fd->ctx->eloop, fd->fd, 1);
+}
+
 int
 dhcpcd_handleargs(struct dhcpcd_ctx *ctx, struct fd_list *fd,
     int argc, char **argv)
@@ -1054,53 +1116,24 @@ dhcpcd_handleargs(struct dhcpcd_ctx *ctx, struct fd_list *fd,
 	int do_exit = 0, do_release = 0, do_reboot = 0;
 	int opt, oi = 0;
 	size_t len, l;
-	struct iovec iov[2];
 	char *tmp, *p;
 
 	if (fd != NULL) {
-		/* Special commands for our control socket */
+		/* Special commands for our control socket
+		 * as the other end should be blocking until it gets the
+		 * expected reply we should be safely able just to change the
+		 * write callback on the fd */
 		if (strcmp(*argv, "--version") == 0) {
-			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, "writev: %m");
-				return -1;
-			}
+			eloop_event_add(fd->ctx->eloop, fd->fd, NULL, NULL,
+			    dhcpcd_version, fd);
 			return 0;
 		} else if (strcmp(*argv, "--getconfigfile") == 0) {
-			len = strlen(ctx->cffile) + 1;
-			iov[0].iov_base = &len;
-			iov[0].iov_len = sizeof(ssize_t);
-			iov[1].iov_base = UNCONST(ctx->cffile);
-			iov[1].iov_len = len;
-			if (writev(fd->fd, iov, 2) == -1) {
-				syslog(LOG_ERR, "writev: %m");
-				return -1;
-			}
+			eloop_event_add(fd->ctx->eloop, fd->fd, NULL, NULL,
+			    dhcpcd_getconfigfile, fd);
 			return 0;
 		} else if (strcmp(*argv, "--getinterfaces") == 0) {
-			len = 0;
-			TAILQ_FOREACH(ifp, ctx->ifaces, next) {
-				len++;
-				if (D_STATE_RUNNING(ifp))
-					len++;
-				if (D6_STATE_RUNNING(ifp))
-					len++;
-				if (ipv6nd_hasra(ifp))
-					len++;
-			}
-			if (write(fd->fd, &len, sizeof(len)) !=
-			    sizeof(len))
-				return -1;
-			TAILQ_FOREACH(ifp, ctx->ifaces, next) {
-				if (send_interface(fd->fd, ifp) == -1)
-					syslog(LOG_ERR,
-					    "send_interface %d: %m",
-					    fd->fd);
-			}
+			eloop_event_add(fd->ctx->eloop, fd->fd, NULL, NULL,
+			    dhcpcd_getinterfaces, fd);
 			return 0;
 		} else if (strcmp(*argv, "--listen") == 0) {
 			fd->listener = 1;
@@ -1598,7 +1631,8 @@ main(int argc, char **argv)
 	if (ctx.link_fd == -1)
 		syslog(LOG_ERR, "open_link_socket: %m");
 	else
-		eloop_event_add(ctx.eloop, ctx.link_fd, handle_link, &ctx);
+		eloop_event_add(ctx.eloop, ctx.link_fd,
+		    handle_link, &ctx, NULL, NULL);
 
 	/* Start any dev listening plugin which may want to
 	 * change the interface name provided by the kernel */
@@ -1688,7 +1722,7 @@ exit1:
 	}
 	free(ctx.duid);
 	if (ctx.link_fd != -1) {
-		eloop_event_delete(ctx.eloop, ctx.link_fd);
+		eloop_event_delete(ctx.eloop, ctx.link_fd, 0);
 		close(ctx.link_fd);
 	}