Re: [PATCH] log: Send identifier string in log messages, openlog() won't work for us

[David Gibson <david@gibson.dropbear.id.au>]

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On Thu, Feb 23, 2023 at 06:35:55PM +0100, Stefano Brivio wrote:
> openlog() can be used to set "ident" and have all the log messages
> prefixed by it, but only if we call syslog() -- this is implemented
> by C libraries.
> 
> We don't log messages with syslog(), though, as we have a custom
> implementation to ensure we don't need dynamic memory allocation.
> This means that it's perfectly useless to call openlog(), and that we
> have to prefix every message we log by the identifier on our own.
> 
> Reported-by: Andrea Bolognani <abologna@redhat.com>
> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

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

> ---
>  log.c | 12 +++++-------
>  1 file changed, 5 insertions(+), 7 deletions(-)
> 
> diff --git a/log.c b/log.c
> index f23e8ef..bfde6ce 100644
> --- a/log.c
> +++ b/log.c
> @@ -106,7 +106,7 @@ void trace_init(int enable)
>  }
>  
>  /**
> - * __openlog() - Non-optional openlog() wrapper, to allow custom vsyslog()
> + * __openlog() - Non-optional openlog() implementation, for custom vsyslog()
>   * @ident:	openlog() identity (program name)
>   * @option:	openlog() options
>   * @facility:	openlog() facility (LOG_DAEMON)
> @@ -136,8 +136,6 @@ void __openlog(const char *ident, int option, int facility)
>  	log_mask |= facility;
>  	strncpy(log_ident, ident, sizeof(log_ident) - 1);
>  	log_opt = option;
> -
> -	openlog(ident, option, facility);
>  }
>  
>  /**
> @@ -158,11 +156,11 @@ void __setlogmask(int mask)
>   */
>  void passt_vsyslog(int pri, const char *format, va_list ap)
>  {
> +	int prefix_len, n;
>  	char buf[BUFSIZ];
> -	int n;
>  
> -	/* Send without name and timestamp, the system logger should add them */
> -	n = snprintf(buf, BUFSIZ, "<%i> ", pri);
> +	/* Send without timestamp, the system logger should add it */
> +	n = prefix_len = snprintf(buf, BUFSIZ, "<%i> %s: ", pri, log_ident);
>  
>  	n += vsnprintf(buf + n, BUFSIZ - n, format, ap);
>  
> @@ -170,7 +168,7 @@ void passt_vsyslog(int pri, const char *format, va_list ap)
>  		n += snprintf(buf + n, BUFSIZ - n, "\n");
>  
>  	if (log_opt & LOG_PERROR)
> -		fprintf(stderr, "%s", buf + sizeof("<0>"));
> +		fprintf(stderr, "%s", buf + prefix_len);
>  
>  	if (send(log_sock, buf, n, 0) != n)
>  		fprintf(stderr, "Failed to send %i bytes to syslog\n", n);

-- 
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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