[PATCH] log: Don't duplicate messages on stderr before daemonising

[PATCH] log: Don't duplicate messages on stderr before daemonising

[Stefano Brivio]

Now that logging functions force printing messages to stderr before
passt forks to background, we'll have duplicate messages when running
from an interactive terminal, or if --stderr is passed, because at
some point we set LOG_PERROR in our __openlog() wrapper.

We could defer setting LOG_PERROR, but that would change option
semantics in other, unexpected ways. We could force calling
passt_vsyslog() as long as the mask is set to LOG_EMERG, but that
complicates the logic in logging functions even further.

Go the easy way for now: don't force printing to stderr with
LOG_EMERG if LOG_PERROR is already set. We should seriously consider a
rework of those logging functions at this point.

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
---
This applies on top of Laine's series.

 log.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/log.c b/log.c
index 785bc36..f23e8ef 100644
--- a/log.c
+++ b/log.c
@@ -44,6 +44,8 @@ static char	log_header[BUFSIZ];	/* File header, written back on cuts */
 static time_t	log_start;		/* Start timestamp */
 int		log_trace;		/* --trace mode enabled */
 
+#define BEFORE_DAEMON		(setlogmask(0) == LOG_MASK(LOG_EMERG))
+
 #define logfn(name, level, doexit)					\
 void name(const char *format, ...) {					\
 	struct timespec tp;						\
@@ -56,8 +58,7 @@ void name(const char *format, ...) {					\
 			tp.tv_nsec / (100L * 1000));			\
 	}								\
 									\
-	if ((LOG_MASK(LOG_PRI(level)) & log_mask) ||			\
-	    setlogmask(0) == LOG_MASK(LOG_EMERG)) {			\
+	if ((LOG_MASK(LOG_PRI(level)) & log_mask) || BEFORE_DAEMON) {	\
 		va_start(args, format);					\
 		if (log_file != -1)					\
 			logfile_write(level, format, args);		\
@@ -67,7 +68,7 @@ void name(const char *format, ...) {					\
 	}								\
 									\
 	if ((setlogmask(0) & LOG_MASK(LOG_DEBUG) && log_file == -1) ||	\
-	     setlogmask(0) == LOG_MASK(LOG_EMERG)) {			\
+	    (BEFORE_DAEMON && !(log_opt & LOG_PERROR))) {		\
 		va_start(args, format);					\
 		(void)vfprintf(stderr, format, args); 			\
 		va_end(args);						\
-- 
@@ -44,6 +44,8 @@ static char	log_header[BUFSIZ];	/* File header, written back on cuts */
 static time_t	log_start;		/* Start timestamp */
 int		log_trace;		/* --trace mode enabled */
 
+#define BEFORE_DAEMON		(setlogmask(0) == LOG_MASK(LOG_EMERG))
+
 #define logfn(name, level, doexit)					\
 void name(const char *format, ...) {					\
 	struct timespec tp;						\
@@ -56,8 +58,7 @@ void name(const char *format, ...) {					\
 			tp.tv_nsec / (100L * 1000));			\
 	}								\
 									\
-	if ((LOG_MASK(LOG_PRI(level)) & log_mask) ||			\
-	    setlogmask(0) == LOG_MASK(LOG_EMERG)) {			\
+	if ((LOG_MASK(LOG_PRI(level)) & log_mask) || BEFORE_DAEMON) {	\
 		va_start(args, format);					\
 		if (log_file != -1)					\
 			logfile_write(level, format, args);		\
@@ -67,7 +68,7 @@ void name(const char *format, ...) {					\
 	}								\
 									\
 	if ((setlogmask(0) & LOG_MASK(LOG_DEBUG) && log_file == -1) ||	\
-	     setlogmask(0) == LOG_MASK(LOG_EMERG)) {			\
+	    (BEFORE_DAEMON && !(log_opt & LOG_PERROR))) {		\
 		va_start(args, format);					\
 		(void)vfprintf(stderr, format, args); 			\
 		va_end(args);						\
-- 
2.35.1

Re: [PATCH] log: Don't duplicate messages on stderr before daemonising

[David Gibson]

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On Wed, Feb 15, 2023 at 12:55:29PM +0100, Stefano Brivio wrote:
> Now that logging functions force printing messages to stderr before
> passt forks to background, we'll have duplicate messages when running
> from an interactive terminal, or if --stderr is passed, because at
> some point we set LOG_PERROR in our __openlog() wrapper.
> 
> We could defer setting LOG_PERROR, but that would change option
> semantics in other, unexpected ways. We could force calling
> passt_vsyslog() as long as the mask is set to LOG_EMERG, but that
> complicates the logic in logging functions even further.
> 
> Go the easy way for now: don't force printing to stderr with
> LOG_EMERG if LOG_PERROR is already set. We should seriously consider a
> rework of those logging functions at this point.
> 
> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

> ---
> This applies on top of Laine's series.
> 
>  log.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/log.c b/log.c
> index 785bc36..f23e8ef 100644
> --- a/log.c
> +++ b/log.c
> @@ -44,6 +44,8 @@ static char	log_header[BUFSIZ];	/* File header, written back on cuts */
>  static time_t	log_start;		/* Start timestamp */
>  int		log_trace;		/* --trace mode enabled */
>  
> +#define BEFORE_DAEMON		(setlogmask(0) == LOG_MASK(LOG_EMERG))
> +
>  #define logfn(name, level, doexit)					\
>  void name(const char *format, ...) {					\
>  	struct timespec tp;						\
> @@ -56,8 +58,7 @@ void name(const char *format, ...) {					\
>  			tp.tv_nsec / (100L * 1000));			\
>  	}								\
>  									\
> -	if ((LOG_MASK(LOG_PRI(level)) & log_mask) ||			\
> -	    setlogmask(0) == LOG_MASK(LOG_EMERG)) {			\
> +	if ((LOG_MASK(LOG_PRI(level)) & log_mask) || BEFORE_DAEMON) {	\
>  		va_start(args, format);					\
>  		if (log_file != -1)					\
>  			logfile_write(level, format, args);		\
> @@ -67,7 +68,7 @@ void name(const char *format, ...) {					\
>  	}								\
>  									\
>  	if ((setlogmask(0) & LOG_MASK(LOG_DEBUG) && log_file == -1) ||	\
> -	     setlogmask(0) == LOG_MASK(LOG_EMERG)) {			\
> +	    (BEFORE_DAEMON && !(log_opt & LOG_PERROR))) {		\
>  		va_start(args, format);					\
>  		(void)vfprintf(stderr, format, args); 			\
>  		va_end(args);						\

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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