detach stdin/stdout/stderr from child processes, implement a separate logging pipe and relay log messages with prefix

1 files changed, 102 insertions, 5 deletions

diff --git a/main.c b/main.c
index 6419fe9..b07784e 100644
--- a/main.c
+++ b/main.c
@@ -3,6 +3,7 @@
 #include <string.h>
 #include <getopt.h>
 #include <unistd.h>
+#include <signal.h>
 
 #include "netifd.h"
 #include "ubus.h"
@@ -19,11 +20,83 @@ static struct list_head process_list = LIST_HEAD_INIT(process_list);
 static struct list_head fds = LIST_HEAD_INIT(fds);
 
 static void
+netifd_delete_process(struct netifd_process *proc)
+{
+	if (proc->uloop.pending)
+		uloop_process_delete(&proc->uloop);
+	list_del(&proc->list);
+	netifd_fd_delete(&proc->log_fd);
+}
+
+static void
+netifd_process_log_cb(struct uloop_fd *fd, unsigned int events)
+{
+	struct netifd_process *proc;
+	const char *log_prefix;
+	char *buf, *cur;
+	int maxlen, len, read_len;
+
+	proc = container_of(fd, struct netifd_process, log_uloop);
+
+	if (!proc->log_buf)
+		proc->log_buf = malloc(LOG_BUF_SIZE + 1);
+
+	buf = proc->log_buf + proc->log_buf_ofs;
+	maxlen = LOG_BUF_SIZE - proc->log_buf_ofs;
+
+	log_prefix = proc->log_prefix;
+	if (!log_prefix)
+		log_prefix = "process";
+
+retry:
+	read_len = len = read(fd->fd, buf, maxlen);
+	if (len <= 0) {
+		if (errno == EINTR)
+			goto retry;
+
+		return;
+	}
+	proc->log_buf_ofs += len;
+
+	cur = buf;
+	buf = proc->log_buf;
+	while ((cur = memchr(cur, '\n', len))) {
+		*cur = 0;
+
+		if (!proc->log_overflow)
+			fprintf(stderr, "%s (%d): %s\n", log_prefix, proc->uloop.pid, buf);
+		else
+			proc->log_overflow = false;
+
+		cur++;
+		len -= cur - buf;
+		buf = cur;
+	}
+
+	if (buf > proc->log_buf && len > 0)
+		memmove(buf, proc->log_buf, len);
+
+	if (len == LOG_BUF_SIZE) {
+		if (!proc->log_overflow) {
+			proc->log_buf[LOG_BUF_SIZE] = 0;
+			fprintf(stderr, "%s (%d): %s [...]\n", log_prefix, proc->uloop.pid, proc->log_buf);
+			proc->log_overflow = true;
+		}
+		len = 0;
+	}
+	proc->log_buf_ofs = len;
+
+	if (read_len == maxlen)
+		goto retry;
+}
+
+static void
 netifd_process_cb(struct uloop_process *proc, int ret)
 {
 	struct netifd_process *np;
 	np = container_of(proc, struct netifd_process, uloop);
-	list_del(&np->list);
+	netifd_process_log_cb(&np->log_uloop, 0);
+	netifd_delete_process(np);
 	return np->cb(np, ret);
 }
 
@@ -31,13 +104,17 @@ int
 netifd_start_process(const char **argv, char **env, struct netifd_process *proc)
 {
 	struct netifd_fd *fd;
+	int pfds[2];
 	int pid;
 
 	netifd_kill_process(proc);
 
-	if ((pid = fork()) < 0)
+	if (pipe(pfds) < 0)
 		return -1;
 
+	if ((pid = fork()) < 0)
+		goto error;
+
 	if (!pid) {
 		if (env) {
 			while (*env) {
@@ -55,19 +132,37 @@ netifd_start_process(const char **argv, char **env, struct netifd_process *proc)
 			close(fd->fd);
 		}
 
+		dup2(pfds[1], 0);
+		dup2(pfds[1], 1);
+		dup2(pfds[1], 2);
+
+		close(pfds[0]);
+		close(pfds[1]);
+
 		execvp(argv[0], (char **) argv);
 		exit(127);
 	}
 
 	if (pid < 0)
-		return -1;
+		goto error;
 
+	close(pfds[1]);
 	proc->uloop.cb = netifd_process_cb;
 	proc->uloop.pid = pid;
 	uloop_process_add(&proc->uloop);
 	list_add_tail(&proc->list, &process_list);
 
+	proc->log_uloop.fd = proc->log_fd.fd = pfds[0];
+	proc->log_uloop.cb = netifd_process_log_cb;
+	netifd_fd_add(&proc->log_fd);
+	uloop_fd_add(&proc->log_uloop, ULOOP_EDGE_TRIGGER | ULOOP_READ);
+
 	return 0;
+
+error:
+	close(pfds[0]);
+	close(pfds[1]);
+	return -1;
 }
 
 void
@@ -77,8 +172,7 @@ netifd_kill_process(struct netifd_process *proc)
 		return;
 
 	kill(proc->uloop.pid, SIGTERM);
-	uloop_process_delete(&proc->uloop);
-	list_del(&proc->list);
+	netifd_delete_process(proc);
 }
 
 void
@@ -151,6 +245,9 @@ netifd_setup_signals(void)
 	sigaction(SIGTERM, &s, NULL);
 	sigaction(SIGUSR1, &s, NULL);
 	sigaction(SIGUSR2, &s, NULL);
+
+	s.sa_handler = SIG_IGN;
+	sigaction(SIGPIPE, &s, NULL);
 }
 
 static void