svn commit: r343827 - head/lib/libcasper/services/cap_syslog

[Jason A. Harmening]

Author: jah
Date: Wed Feb  6 04:36:28 2019
New Revision: 343827
URL: https://svnweb.freebsd.org/changeset/base/343827

Log:
  r341692 changed cap_syslog(3) to preserve the stdio descriptors inherited
  from its parent so that LOG_PERROR would work.  However, this caused
  dhclient(8)'s stdio streams to remain open across daemonization, breaking
  the ability to capture its foreground output as done in netconfig_ipv4.
  
  Fix this by reverting r341692 and instead passing the parent's stderr
  descriptor as an argument to cap_openlog() only when LOG_PERROR is specified
  in logopt.
  
  PR:	234514
  Suggested by:	markj
  Reported by:	Shawn Webb
  Reviewed by:	markj, oshogbo
  MFC after:	2 weeks
  Differential Revision:	https://reviews.freebsd.org/D18989

Modified:
  head/lib/libcasper/services/cap_syslog/cap_syslog.c

Modified: head/lib/libcasper/services/cap_syslog/cap_syslog.c
==============================================================================
--- head/lib/libcasper/services/cap_syslog/cap_syslog.c	Wed Feb  6 04:00:37 2019	(r343826)
+++ head/lib/libcasper/services/cap_syslog/cap_syslog.c	Wed Feb  6 04:36:28 2019	(r343827)
@@ -88,6 +88,9 @@ cap_openlog(cap_channel_t *chan, const char *ident, in
 	}
 	nvlist_add_number(nvl, "logopt", logopt);
 	nvlist_add_number(nvl, "facility", facility);
+	if (logopt & LOG_PERROR) {
+		nvlist_add_descriptor(nvl, "stderr", STDERR_FILENO);
+	}
 	nvl = cap_xfer_nvlist(chan, nvl);
 	if (nvl == NULL) {
 		return;
@@ -131,6 +134,7 @@ cap_setlogmask(cap_channel_t *chan, int maskpri)
  */
 
 static char *LogTag;
+static int prev_stderr = -1;
 
 static void
 slog_vsyslog(const nvlist_t *limits __unused, const nvlist_t *nvlin,
@@ -146,6 +150,8 @@ slog_openlog(const nvlist_t *limits __unused, const nv
     nvlist_t *nvlout __unused)
 {
 	const char *ident;
+	uint64_t logopt;
+	int stderr_fd;
 
 	ident = dnvlist_get_string(nvlin, "ident", NULL);
 	if (ident != NULL) {
@@ -153,8 +159,19 @@ slog_openlog(const nvlist_t *limits __unused, const nv
 		LogTag = strdup(ident);
 	}
 
-	openlog(LogTag, nvlist_get_number(nvlin, "logopt"),
-	    nvlist_get_number(nvlin, "facility"));
+	logopt = nvlist_get_number(nvlin, "logopt");
+	if (logopt & LOG_PERROR) {
+		stderr_fd = dnvlist_get_descriptor(nvlin, "stderr", -1);
+		if (prev_stderr == -1)
+			prev_stderr = dup(STDERR_FILENO);
+		if (prev_stderr != -1)
+			(void)dup2(stderr_fd, STDERR_FILENO);
+	} else if (prev_stderr != -1) {
+		(void)dup2(prev_stderr, STDERR_FILENO);
+		close(prev_stderr);
+		prev_stderr = -1;
+	}
+	openlog(LogTag, logopt, nvlist_get_number(nvlin, "facility"));
 }
 
 static void
@@ -166,6 +183,12 @@ slog_closelog(const nvlist_t *limits __unused, const n
 
 	free(LogTag);
 	LogTag = NULL;
+
+	if (prev_stderr != -1) {
+		(void)dup2(prev_stderr, STDERR_FILENO);
+		close(prev_stderr);
+		prev_stderr = -1;
+	}
 }
 
 static void
@@ -198,4 +221,4 @@ syslog_command(const char *cmd, const nvlist_t *limits
 	return (0);
 }
 
-CREATE_SERVICE("system.syslog", NULL, syslog_command, CASPER_SERVICE_STDIO);
+CREATE_SERVICE("system.syslog", NULL, syslog_command, 0);