The message from usage() when given invalid options, or the -h / --help
option is currently printed by many calls to the info() function, also
used for runtime logging of informational messages.

That isn't useful: the usage message should always go to the terminal
(stdout or stderr), never syslog or a logfile.  It should never be
filtered by priority.  Really the only thing using the common logging
functions does is give more opportunities for something to go wrong.

Replace all the info() calls with direct fprintf() calls.  This does mean
manually adding "\n" to each message.  A little messy, but worth it for the
simplicity in other dimensions.  While we're there make much heavier use
of single strings containing multiple lines of output text.  That reduces
the number of fprintf calls, reducing visual clutter and making it easier
to see what the output will look like from the source.

Link: https://bugs.passt.top/show_bug.cgi?id=90

Signed-off-by: David Gibson <david(a)gibson.dropbear.id.au>
---
 conf.c | 326 +++++++++++++++++++++++++++++----------------------------
 1 file changed, 166 insertions(+), 160 deletions(-)

diff --git a/conf.c b/conf.c
index f2a92574..72ca1fc8 100644
--- a/conf.c
+++ b/conf.c
@@ -706,193 +706,200 @@ static unsigned int conf_ip6(unsigned int ifi,
 /**
  * usage() - Print usage, exit with given status code
  * @name:	Executable name
+ * @f:		Stream to print usage info to
  * @status:	Status code for exit()
  */
-static void usage(const char *name, int status)
+static void usage(const char *name, FILE *f, int status)
 {
 	if (strstr(name, "pasta")) {
-		info("Usage: %s [OPTION]... [COMMAND] [ARGS]...", name);
-		info("       %s [OPTION]... PID", name);
-		info("       %s [OPTION]... --netns [PATH|NAME]", name);
-		info("");
-		info("Without PID or --netns, run the given command or a");
-		info("default shell in a new network and user namespace, and");
-		info("connect it via pasta.");
+		fprintf(f, "Usage: %s [OPTION]... [COMMAND] [ARGS]...\n", name);
+		fprintf(f, "       %s [OPTION]... PID\n", name);
+		fprintf(f, "       %s [OPTION]... --netns [PATH|NAME]\n", name);
+		fprintf(f,
+			"\n"
+			"Without PID or --netns, run the given command or a\n"
+			"default shell in a new network and user namespace, and\n"
+			"connect it via pasta.\n");
 	} else {
-		info("Usage: %s [OPTION]...", name);
+		fprintf(f, "Usage: %s [OPTION]...\n", name);
 	}
-	info("");
-
-
-	info(   "  -d, --debug		Be verbose");
-	info(   "      --trace		Be extra verbose, implies --debug");
-	info(   "  -q, --quiet		Don't print informational messages");
-	info(   "  -f, --foreground	Don't run in background");
-	info(   "    default: run in background if started from a TTY");
-	info(   "  -e, --stderr		Log to stderr too");
-	info(   "    default: log to system logger only if started from a TTY");
-	info(   "  -l, --log-file PATH	Log (only) to given file");
-	info(   "  --log-size BYTES	Maximum size of log file");
-	info(   "    default: 1 MiB");
-	info(   "  --runas UID|UID:GID 	Run as given UID, GID, which can be");
-	info(   "    numeric, or login and group names");
-	info(   "    default: drop to user \"nobody\"");
-	info(   "  -h, --help		Display this help message and exit");
-	info(   "  --version		Show version and exit");
+
+	fprintf(f,
+		"\n"
+		"  -d, --debug		Be verbose\n"
+		"      --trace		Be extra verbose, implies --debug\n"
+		"  -q, --quiet		Don't print informational messages\n"
+		"  -f, --foreground	Don't run in background\n"
+		"    default: run in background if started from a TTY\n"
+		"  -e, --stderr		Log to stderr too\n"
+		"    default: log to system logger only if started from a TTY\n"
+		"  -l, --log-file PATH	Log (only) to given file\n"
+		"  --log-size BYTES	Maximum size of log file\n"
+		"    default: 1 MiB\n"
+		"  --runas UID|UID:GID 	Run as given UID, GID, which can be\n"
+		"    numeric, or login and group names\n"
+		"    default: drop to user \"nobody\"\n"
+		"  -h, --help		Display this help message and exit\n"
+		"  --version		Show version and exit\n");
 
 	if (strstr(name, "pasta")) {
-		info(   "  -I, --ns-ifname NAME	namespace interface name");
-		info(   "    default: same interface name as external one");
+		fprintf(f,
+			"  -I, --ns-ifname NAME	namespace interface name\n"
+			"    default: same interface name as external one\n");
 	} else {
-		info(   "  -s, --socket PATH	UNIX domain socket path");
-		info(   "    default: probe free path starting from "
-		     UNIX_SOCK_PATH, 1);
+		fprintf(f,
+			"  -s, --socket PATH	UNIX domain socket path\n"
+			"    default: probe free path starting from "
+			UNIX_SOCK_PATH "\n", 1);
 	}
 
-	info(   "  -F, --fd FD		Use FD as pre-opened connected socket");
-	info(   "  -p, --pcap FILE	Log tap-facing traffic to pcap file");
-	info(   "  -P, --pid FILE	Write own PID to the given file");
-	info(   "  -m, --mtu MTU	Assign MTU via DHCP/NDP");
-	info(   "    a zero value disables assignment");
-	info(   "    default: 65520: maximum 802.3 MTU minus 802.3 header");
-	info(   "                    length, rounded to 32 bits (IPv4 words)");
-	info(   "  -a, --address ADDR	Assign IPv4 or IPv6 address ADDR");
-	info(   "    can be specified zero to two times (for IPv4 and IPv6)");
-	info(   "    default: use addresses from interface with default route");
-	info(   "  -n, --netmask MASK	Assign IPv4 MASK, dot-decimal or bits");
-	info(   "    default: netmask from matching address on the host");
-	info(   "  -M, --mac-addr ADDR	Use source MAC address ADDR");
-	info(   "    default: MAC address from interface with default route");
-	info(   "  -g, --gateway ADDR	Pass IPv4 or IPv6 address as gateway");
-	info(   "    default: gateway from interface with default route");
-	info(   "  -i, --interface NAME	Interface for addresses and routes");
-	info(   "    default: from --outbound-if4 and --outbound-if6, if any");
-	info(   "             otherwise interface with first default route");
-	info(   "  -o, --outbound ADDR	Bind to address as outbound source");
-	info(   "    can be specified zero to two times (for IPv4 and IPv6)");
-	info(   "    default: use source address from routing tables");
-	info(   "  --outbound-if4 NAME	Bind to outbound interface for IPv4");
-	info(   "    default: use interface from default route");
-	info(   "  --outbound-if6 NAME	Bind to outbound interface for IPv6");
-	info(   "    default: use interface from default route");
-	info(   "  -D, --dns ADDR	Use IPv4 or IPv6 address as DNS");
-	info(   "    can be specified multiple times");
-	info(   "    a single, empty option disables DNS information");
+	fprintf(f,
+		"  -F, --fd FD		Use FD as pre-opened connected socket\n"
+		"  -p, --pcap FILE	Log tap-facing traffic to pcap file\n"
+		"  -P, --pid FILE	Write own PID to the given file\n"
+		"  -m, --mtu MTU	Assign MTU via DHCP/NDP\n"
+		"    a zero value disables assignment\n"
+		"    default: 65520: maximum 802.3 MTU minus 802.3 header\n"
+		"                    length, rounded to 32 bits (IPv4 words)\n"
+		"  -a, --address ADDR	Assign IPv4 or IPv6 address ADDR\n"
+		"    can be specified zero to two times (for IPv4 and IPv6)\n"
+		"    default: use addresses from interface with default route\n"
+		"  -n, --netmask MASK	Assign IPv4 MASK, dot-decimal or bits\n"
+		"    default: netmask from matching address on the host\n"
+		"  -M, --mac-addr ADDR	Use source MAC address ADDR\n"
+		"    default: MAC address from interface with default route\n"
+		"  -g, --gateway ADDR	Pass IPv4 or IPv6 address as gateway\n"
+		"    default: gateway from interface with default route\n"
+		"  -i, --interface NAME	Interface for addresses and routes\n"
+		"    default: from --outbound-if4 and --outbound-if6, if any\n"
+		"             otherwise interface with first default route\n"
+		"  -o, --outbound ADDR	Bind to address as outbound source\n"
+		"    can be specified zero to two times (for IPv4 and IPv6)\n"
+		"    default: use source address from routing tables\n"
+		"  --outbound-if4 NAME	Bind to outbound interface for IPv4\n"
+		"    default: use interface from default route\n"
+		"  --outbound-if6 NAME	Bind to outbound interface for IPv6\n"
+		"    default: use interface from default route\n"
+		"  -D, --dns ADDR	Use IPv4 or IPv6 address as DNS\n"
+		"    can be specified multiple times\n"
+		"    a single, empty option disables DNS information\n");
 	if (strstr(name, "pasta"))
-		info(   "    default: don't use any addresses");
+		fprintf(f, "    default: don't use any addresses\n");
 	else
-		info(   "    default: use addresses from /etc/resolv.conf");
-
-	info(   "  -S, --search LIST	Space-separated list, search domains");
-	info(   "    a single, empty option disables the DNS search list");
+		fprintf(f, "    default: use addresses from /etc/resolv.conf\n");
+	fprintf(f,
+		"  -S, --search LIST	Space-separated list, search domains\n"
+		"    a single, empty option disables the DNS search list\n");
 	if (strstr(name, "pasta"))
-		info(   "    default: don't use any search list");
+		fprintf(f, "    default: don't use any search list\n");
 	else
-		info(   "    default: use search list from /etc/resolv.conf");
+		fprintf(f, "    default: use search list from /etc/resolv.conf\n");
 
 	if (strstr(name, "pasta"))
-		info("  --dhcp-dns	\tPass DNS list via DHCP/DHCPv6/NDP");
+		fprintf(f, "  --dhcp-dns	\tPass DNS list via DHCP/DHCPv6/NDP\n");
 	else
-		info("  --no-dhcp-dns	No DNS list in DHCP/DHCPv6/NDP");
+		fprintf(f, "  --no-dhcp-dns	No DNS list in DHCP/DHCPv6/NDP\n");
 
 	if (strstr(name, "pasta"))
-		info("  --dhcp-search	Pass list via DHCP/DHCPv6/NDP");
+		fprintf(f, "  --dhcp-search	Pass list via DHCP/DHCPv6/NDP\n");
 	else
-		info("  --no-dhcp-search	No list in DHCP/DHCPv6/NDP");
-
-	info(   "  --dns-forward ADDR	Forward DNS queries sent to ADDR");
-	info(   "    can be specified zero to two times (for IPv4 and IPv6)");
-	info(   "    default: don't forward DNS queries");
-
-	info(   "  --no-tcp		Disable TCP protocol handler");
-	info(   "  --no-udp		Disable UDP protocol handler");
-	info(   "  --no-icmp		Disable ICMP/ICMPv6 protocol handler");
-	info(   "  --no-dhcp		Disable DHCP server");
-	info(   "  --no-ndp		Disable NDP responses");
-	info(   "  --no-dhcpv6		Disable DHCPv6 server");
-	info(   "  --no-ra		Disable router advertisements");
-	info(   "  --no-map-gw		Don't map gateway address to host");
-	info(   "  -4, --ipv4-only	Enable IPv4 operation only");
-	info(   "  -6, --ipv6-only	Enable IPv6 operation only");
+		fprintf(f, "  --no-dhcp-search	No list in DHCP/DHCPv6/NDP\n");
+
+	fprintf(f,
+		"  --dns-forward ADDR	Forward DNS queries sent to ADDR\n"
+		"    can be specified zero to two times (for IPv4 and IPv6)\n"
+		"    default: don't forward DNS queries\n"
+		"  --no-tcp		Disable TCP protocol handler\n"
+		"  --no-udp		Disable UDP protocol handler\n"
+		"  --no-icmp		Disable ICMP/ICMPv6 protocol handler\n"
+		"  --no-dhcp		Disable DHCP server\n"
+		"  --no-ndp		Disable NDP responses\n"
+		"  --no-dhcpv6		Disable DHCPv6 server\n"
+		"  --no-ra		Disable router advertisements\n"
+		"  --no-map-gw		Don't map gateway address to host\n"
+		"  -4, --ipv4-only	Enable IPv4 operation only\n"
+		"  -6, --ipv6-only	Enable IPv6 operation only\n");
 
 	if (strstr(name, "pasta"))
 		goto pasta_opts;
 
-	info(   "  -1, --one-off	Quit after handling one single client");
-	info(   "  -t, --tcp-ports SPEC	TCP port forwarding to guest");
-	info(   "    can be specified multiple times");
-	info(   "    SPEC can be:");
-	info(   "      'none': don't forward any ports");
-	info(   "      'all': forward all unbound, non-ephemeral ports");
-	info(   "      a comma-separated list, optionally ranged with
'-'");
-	info(   "        and optional target ports after ':', with
optional");
-	info(   "        address specification suffixed by '/' and
optional");
-	info(   "        interface prefixed by '%%'. Ranges can be reduced
by");
-	info(   "        excluding ports or ranges prefixed by '~'");
-	info(   "        Examples:");
-	info(   "        -t 22		Forward local port 22 to 22 on guest");
-	info(   "        -t 22:23	Forward local port 22 to 23 on guest");
-	info(   "        -t 22,25	Forward ports 22, 25 to ports 22, 25");
-	info(   "        -t 22-80  	Forward ports 22 to 80");
-	info(   "        -t 22-80:32-90	Forward ports 22 to 80 to");
-	info(   "			corresponding port numbers plus 10");
-	info(   "        -t 192.0.2.1/5	Bind port 5 of 192.0.2.1 to guest");
-	info(   "        -t 5-25,~10-20	Forward ports 5 to 9, and 21 to 25");
-	info(   "        -t ~25		Forward all ports except for 25");
-	info(   "    default: none");
-	info(   "  -u, --udp-ports SPEC	UDP port forwarding to guest");
-	info(   "    SPEC is as described for TCP above");
-	info(   "    default: none");
+	fprintf(f,
+		"  -1, --one-off	Quit after handling one single client\n"
+		"  -t, --tcp-ports SPEC	TCP port forwarding to guest\n"
+		"    can be specified multiple times\n"
+		"    SPEC can be:\n"
+		"      'none': don't forward any ports\n"
+		"      'all': forward all unbound, non-ephemeral ports\n"
+		"      a comma-separated list, optionally ranged with '-'\n"
+		"        and optional target ports after ':', with optional\n"
+		"        address specification suffixed by '/' and optional\n"
+		"        interface prefixed by '%%'. Ranges can be reduced by\n"
+		"        excluding ports or ranges prefixed by '~'\n"
+		"        Examples:\n"
+		"        -t 22		Forward local port 22 to 22 on guest\n"
+		"        -t 22:23	Forward local port 22 to 23 on guest\n"
+		"        -t 22,25	Forward ports 22, 25 to ports 22, 25\n"
+		"        -t 22-80  	Forward ports 22 to 80\n"
+		"        -t 22-80:32-90	Forward ports 22 to 80 to\n"
+		"			corresponding port numbers plus 10\n"
+		"        -t 192.0.2.1/5	Bind port 5 of 192.0.2.1 to guest\n"
+		"        -t 5-25,~10-20	Forward ports 5 to 9, and 21 to 25\n"
+		"        -t ~25		Forward all ports except for 25\n"
+		"    default: none\n"
+		"  -u, --udp-ports SPEC	UDP port forwarding to guest\n"
+		"    SPEC is as described for TCP above\n"
+		"    default: none\n");
 
 	exit(status);
 
 pasta_opts:
 
-	info(   "  -t, --tcp-ports SPEC	TCP port forwarding to namespace");
-	info(   "    can be specified multiple times"); 
-	info(   "    SPEC can be:");
-	info(   "      'none': don't forward any ports");
-	info(   "      'auto': forward all ports currently bound in
namespace");
-	info(   "      a comma-separated list, optionally ranged with
'-'");
-	info(   "        and optional target ports after ':', with
optional");
-	info(   "        address specification suffixed by '/' and
optional");
-	info(   "        interface prefixed by '%%'. Examples:");
-	info(   "        -t 22	Forward local port 22 to port 22 in netns");
-	info(   "        -t 22:23	Forward local port 22 to port 23");
-	info(   "        -t 22,25	Forward ports 22, 25 to ports 22, 25");
-	info(   "        -t 22-80	Forward ports 22 to 80");
-	info(   "        -t 22-80:32-90	Forward ports 22 to 80 to");
-	info(   "			corresponding port numbers plus 10");
-	info(   "        -t 192.0.2.1/5	Bind port 5 of 192.0.2.1 to namespace");
-	info(   "        -t 5-25,~10-20	Forward ports 5 to 9, and 21 to 25");
-	info(   "        -t ~25		Forward all bound ports except for 25");
-	info(   "    default: auto");
-	info(   "    IPv6 bound ports are also forwarded for IPv4");
-	info(   "  -u, --udp-ports SPEC	UDP port forwarding to namespace");
-	info(   "    SPEC is as described for TCP above");
-	info(   "    default: auto");
-	info(   "    IPv6 bound ports are also forwarded for IPv4");
-	info(   "    unless specified, with '-t auto', UDP ports with
numbers");
-	info(   "    corresponding to forwarded TCP port numbers are");
-	info(   "    forwarded too");
-	info(   "  -T, --tcp-ns SPEC	TCP port forwarding to init namespace");
-	info(   "    SPEC is as described above");
-	info(   "    default: auto");
-	info(   "  -U, --udp-ns SPEC	UDP port forwarding to init namespace");
-	info(   "    SPEC is as described above");
-	info(   "    default: auto");
-	info(   "  --userns NSPATH 	Target user namespace to join");
-	info(   "  --netns PATH|NAME	Target network namespace to join");
-	info(   "  --netns-only		Don't join existing user namespace");
-	info(   "    implied if PATH or NAME are given without --userns");
-	info(   "  --no-netns-quit	Don't quit if filesystem-bound target");
-	info(   "  			network namespace is deleted");
-	info(   "  --config-net		Configure tap interface in namespace");
-	info(   "  --no-copy-routes	DEPRECATED:");
-	info(   "			Don't copy all routes to namespace");
-	info(   "  --no-copy-addrs	DEPRECATED:");
-	info(   "			Don't copy all addresses to namespace");
-	info(   "  --ns-mac-addr ADDR	Set MAC address on tap interface");
+	fprintf(f,
+		"  -t, --tcp-ports SPEC	TCP port forwarding to namespace\n"
+		"    can be specified multiple times\n"
+		"    SPEC can be:\n"
+		"      'none': don't forward any ports\n"
+		"      'auto': forward all ports currently bound in namespace\n"
+		"      a comma-separated list, optionally ranged with '-'\n"
+		"        and optional target ports after ':', with optional\n"
+		"        address specification suffixed by '/' and optional\n"
+		"        interface prefixed by '%%'. Examples:\n"
+		"        -t 22	Forward local port 22 to port 22 in netns\n"
+		"        -t 22:23	Forward local port 22 to port 23\n"
+		"        -t 22,25	Forward ports 22, 25 to ports 22, 25\n"
+		"        -t 22-80	Forward ports 22 to 80\n"
+		"        -t 22-80:32-90	Forward ports 22 to 80 to\n"
+		"			corresponding port numbers plus 10\n"
+		"        -t 192.0.2.1/5	Bind port 5 of 192.0.2.1 to namespace\n"
+		"        -t 5-25,~10-20	Forward ports 5 to 9, and 21 to 25\n"
+		"        -t ~25		Forward all bound ports except for 25\n"
+		"    default: auto\n"
+		"    IPv6 bound ports are also forwarded for IPv4\n"
+		"  -u, --udp-ports SPEC	UDP port forwarding to namespace\n"
+		"    SPEC is as described for TCP above\n"
+		"    default: auto\n"
+		"    IPv6 bound ports are also forwarded for IPv4\n"
+		"    unless specified, with '-t auto', UDP ports with numbers\n"
+		"    corresponding to forwarded TCP port numbers are\n"
+		"    forwarded too\n"
+		"  -T, --tcp-ns SPEC	TCP port forwarding to init namespace\n"
+		"    SPEC is as described above\n"
+		"    default: auto\n"
+		"  -U, --udp-ns SPEC	UDP port forwarding to init namespace\n"
+		"    SPEC is as described above\n"
+		"    default: auto\n"
+		"  --userns NSPATH 	Target user namespace to join\n"
+		"  --netns PATH|NAME	Target network namespace to join\n"
+		"  --netns-only		Don't join existing user namespace\n"
+		"    implied if PATH or NAME are given without --userns\n"
+		"  --no-netns-quit	Don't quit if filesystem-bound target\n"
+		"  			network namespace is deleted\n"
+		"  --config-net		Configure tap interface in namespace\n"
+		"  --no-copy-routes	DEPRECATED:\n"
+		"			Don't copy all routes to namespace\n"
+		"  --no-copy-addrs	DEPRECATED:\n"
+		"			Don't copy all addresses to namespace\n"
+		"  --ns-mac-addr ADDR	Set MAC address on tap interface\n");
 
 	exit(status);
 }
@@ -1637,12 +1644,11 @@ void conf(struct ctx *c, int argc, char **argv)
 			/* Handle these later, once addresses are configured */
 			break;
 		case 'h':
-			log_to_stdout = 1;
-			usage(argv[0], EXIT_SUCCESS);
+			usage(argv[0], stdout, EXIT_SUCCESS);
 			break;
 		case '?':
 		default:
-			usage(argv[0], EXIT_FAILURE);
+			usage(argv[0], stderr, EXIT_FAILURE);
 			break;
 		}
 	} while (name != -1);
-- 
2.45.1

On Wed,  5 Jun 2024 10:42:39 +1000
David Gibson <david(a)gibson.dropbear.id.au> wrote:

...
  Erik Sjölund pointed out a regression where we're
no long printing the
 --help message to stdout, but to stderr instead.
 
 I'm not actually sure what caused the regression, but it was made
 possible by the fact that the original fix was pretty strange to begin
 with.  It introduced some hacks to force the logging subsystem to go
 to stdout, which have presumably failed in some subtle way.  But,
 there's really no reason to run usage() through the logging subsystem
 in the first place - it just adds complexity.
 
 Link: https://bugs.passt.top/show_bug.cgi?id=90
 Link: https://bugs.passt.top/show_bug.cgi?id=52
 
 Changes since v1:
  * Use multi-line strings heavily in 2/3
 
 David Gibson (3):
   conf: Remove unhelpful usage() wrapper
   conf: Don't print usage via the logging subsystem
   log: Remove log_to_stdout option 
Applied.

-- 
Stefano