Re: [PATCH v2] conf: Accept duplicate and conflicting options, the last one wins

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

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On Wed, Jun 19, 2024 at 05:40:19PM +0200, Stefano Brivio wrote:
> In multiple occasions, especially when passt(1) and pasta(1) are used
> in integrations such as the one with Podman, the ability to override
> earlier options on the command line with later one would have been
> convenient.
> 
> Recently, to debug a number of issues happening with Podman, I would
> have liked to ask users to share a debug log by passing --debug as
> additional option, but pasta refuses --quiet (always passed by Podman)
> and --debug at the same time.
> 
> On top of this, Podman lets users specify other pasta options in its
> containers.conf(5) file, as well as on the command line.
> 
> The options from the configuration files are appended together with
> the ones from the command line, which makes it impossible for users to
> override options from the configuration file, if duplicated options
> are refused, unless Podman takes care of sorting them, which is
> clearly not sustainable.
> 
> For --debug and --trace, somebody took care of this on Podman side at:
>   https://github.com/containers/common/pull/2052
> 
> but this doesn't fix the issue with other options, and we'll have
> anyway older versions of Podman around, too.
> 
> I think there's some value in telling users about duplicated or
> conflicting options, because that might reveal issues in integrations
> or accidental misconfigurations, but by now I'm fairly convinced that
> the downsides outweigh this.
> 
> Drop checks about duplicate options and mutually exclusive ones. In
> some cases, we need to also undo a couple of initialisations caused
> by earlier options, but this looks like a simplification, overall.
> 
> Notable exception: --stderr still conflicts with --log-file, because
> users might have the expectation that they don't actually conflict.
> But they do conflict in the existing implementation, so it's safer
> to make sure that the users notice that.
> 
> Suggested-by: Paul Holzinger <pholzing@redhat.com>
> Suggested-by: David Gibson <david@gibson.dropbear.id.au>
> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

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

> ---
> v2:
>   - report --log-file and --stderr as conflicting, but accept
>     multiple options if they don't conflict
>   - for --log-file and --pcap, make it clear in the man page that
>     the general principle still applies: only the last one (of each)
>     takes effect
>   - add some more context about Podman and how the list of pasta
>     options is built there, in the commit message
> 
>  conf.c  | 134 ++++++++++++++++----------------------------------------
>  passt.1 |  17 +++++++
>  2 files changed, 55 insertions(+), 96 deletions(-)
> 
> diff --git a/conf.c b/conf.c
> index 94b3ed6..c5f13ac 100644
> --- a/conf.c
> +++ b/conf.c
> @@ -517,9 +517,6 @@ static void conf_netns_opt(char *netns, const char *arg)
>  static void conf_pasta_ns(int *netns_only, char *userns, char *netns,
>  			  int optind, int argc, char *argv[])
>  {
> -	if (*netns_only && *userns)
> -		die("Both --userns and --netns-only given");
> -
>  	if (*netns && optind != argc)
>  		die("Both --netns and PID or command given");
>  
> @@ -1204,7 +1201,6 @@ void conf(struct ctx *c, int argc, char **argv)
>  		{"udp-ns",	required_argument,	NULL,		'U' },
>  		{"userns",	required_argument,	NULL,		2 },
>  		{"netns",	required_argument,	NULL,		3 },
> -		{"netns-only",	no_argument,		&netns_only,	1 },
>  		{"ns-mac-addr",	required_argument,	NULL,		4 },
>  		{"dhcp-dns",	no_argument,		NULL,		5 },
>  		{"no-dhcp-dns",	no_argument,		NULL,		6 },
> @@ -1221,6 +1217,7 @@ void conf(struct ctx *c, int argc, char **argv)
>  		{"config-net",	no_argument,		NULL,		17 },
>  		{"no-copy-routes", no_argument,		NULL,		18 },
>  		{"no-copy-addrs", no_argument,		NULL,		19 },
> +		{"netns-only",	no_argument,		NULL,		20 },
>  		{ 0 },
>  	};
>  	char userns[PATH_MAX] = { 0 }, netns[PATH_MAX] = { 0 };
> @@ -1265,6 +1262,8 @@ void conf(struct ctx *c, int argc, char **argv)
>  			if (ret <= 0 || ret >= (int)sizeof(userns))
>  				die("Invalid userns: %s", optarg);
>  
> +			netns_only = 0;
> +
>  			break;
>  		case 3:
>  			if (c->mode != MODE_PASTA)
> @@ -1325,24 +1324,13 @@ void conf(struct ctx *c, int argc, char **argv)
>  			c->no_netns_quit = 1;
>  			break;
>  		case 11:
> -			if (c->trace)
> -				die("Multiple --trace options given");
> -
> -			if (c->quiet)
> -				die("Either --trace or --quiet");
> -
>  			c->trace = c->debug = 1;
> +			c->quiet = 0;
>  			break;
>  		case 12:
> -			if (runas)
> -				die("Multiple --runas options given");
> -
>  			runas = optarg;
>  			break;
>  		case 13:
> -			if (logsize)
> -				die("Multiple --log-size options given");
> -
>  			errno = 0;
>  			logsize = strtol(optarg, NULL, 0);
>  
> @@ -1356,9 +1344,6 @@ void conf(struct ctx *c, int argc, char **argv)
>  			fprintf(stdout, VERSION_BLOB);
>  			exit(EXIT_SUCCESS);
>  		case 15:
> -			if (*c->ip4.ifname_out)
> -				die("Redundant outbound interface: %s", optarg);
> -
>  			ret = snprintf(c->ip4.ifname_out,
>  				       sizeof(c->ip4.ifname_out), "%s", optarg);
>  			if (ret <= 0 || ret >= (int)sizeof(c->ip4.ifname_out))
> @@ -1366,9 +1351,6 @@ void conf(struct ctx *c, int argc, char **argv)
>  
>  			break;
>  		case 16:
> -			if (*c->ip6.ifname_out)
> -				die("Redundant outbound interface: %s", optarg);
> -
>  			ret = snprintf(c->ip6.ifname_out,
>  				       sizeof(c->ip6.ifname_out), "%s", optarg);
>  			if (ret <= 0 || ret >= (int)sizeof(c->ip6.ifname_out))
> @@ -1395,62 +1377,47 @@ void conf(struct ctx *c, int argc, char **argv)
>  			warn("--no-copy-addrs will be dropped soon");
>  			c->no_copy_addrs = copy_addrs_opt = true;
>  			break;
> -		case 'd':
> -			if (c->debug)
> -				die("Multiple --debug options given");
> -
> -			if (c->quiet)
> -				die("Either --debug or --quiet");
> +		case 20:
> +			if (c->mode != MODE_PASTA)
> +				die("--netns-only is for pasta mode only");
>  
> +			netns_only = 1;
> +			*userns = 0;
> +			break;
> +		case 'd':
>  			c->debug = 1;
> +			c->quiet = 0;
>  			break;
>  		case 'e':
>  			if (logfile)
>  				die("Can't log to both file and stderr");
>  
> -			if (c->force_stderr)
> -				die("Multiple --stderr options given");
> -
>  			c->force_stderr = 1;
> +			logfile = NULL;
>  			break;
>  		case 'l':
>  			if (c->force_stderr)
>  				die("Can't log to both stderr and file");
>  
> -			if (logfile)
> -				die("Multiple --log-file options given");
> -
>  			logfile = optarg;
> +			c->force_stderr = 0;
>  			break;
>  		case 'q':
> -			if (c->quiet)
> -				die("Multiple --quiet options given");
> -
> -			if (c->debug)
> -				die("Either --debug or --quiet");
> -
>  			c->quiet = 1;
> +			c->debug = c->trace = 0;
>  			break;
>  		case 'f':
> -			if (c->foreground)
> -				die("Multiple --foreground options given");
> -
>  			c->foreground = 1;
>  			break;
>  		case 's':
> -			if (*c->sock_path)
> -				die("Multiple --socket options given");
> -
>  			ret = snprintf(c->sock_path, UNIX_SOCK_MAX - 1, "%s",
>  				       optarg);
>  			if (ret <= 0 || ret >= (int)sizeof(c->sock_path))
>  				die("Invalid socket path: %s", optarg);
>  
> +			c->fd_tap = -1;
>  			break;
>  		case 'F':
> -			if (c->fd_tap >= 0)
> -				die("Multiple --fd options given");
> -
>  			errno = 0;
>  			c->fd_tap = strtol(optarg, NULL, 0);
>  
> @@ -1458,12 +1425,9 @@ void conf(struct ctx *c, int argc, char **argv)
>  				die("Invalid --fd: %s", optarg);
>  
>  			c->one_off = true;
> -
> +			*c->sock_path = 0;
>  			break;
>  		case 'I':
> -			if (*c->pasta_ifn)
> -				die("Multiple --ns-ifname options given");
> -
>  			ret = snprintf(c->pasta_ifn, IFNAMSIZ, "%s",
>  				       optarg);
>  			if (ret <= 0 || ret >= IFNAMSIZ)
> @@ -1471,18 +1435,12 @@ void conf(struct ctx *c, int argc, char **argv)
>  
>  			break;
>  		case 'p':
> -			if (*c->pcap)
> -				die("Multiple --pcap options given");
> -
>  			ret = snprintf(c->pcap, sizeof(c->pcap), "%s", optarg);
>  			if (ret <= 0 || ret >= (int)sizeof(c->pcap))
>  				die("Invalid pcap path: %s", optarg);
>  
>  			break;
>  		case 'P':
> -			if (*c->pidfile)
> -				die("Multiple --pid options given");
> -
>  			ret = snprintf(c->pidfile, sizeof(c->pidfile), "%s",
>  				       optarg);
>  			if (ret <= 0 || ret >= (int)sizeof(c->pidfile))
> @@ -1490,9 +1448,6 @@ void conf(struct ctx *c, int argc, char **argv)
>  
>  			break;
>  		case 'm':
> -			if (c->mtu)
> -				die("Multiple --mtu options given");
> -
>  			errno = 0;
>  			c->mtu = strtol(optarg, NULL, 0);
>  
> @@ -1542,14 +1497,12 @@ void conf(struct ctx *c, int argc, char **argv)
>  			if (c->mode == MODE_PASTA)
>  				c->no_copy_routes = 1;
>  
> -			if (IN6_IS_ADDR_UNSPECIFIED(&c->ip6.gw)		&&
> -			    inet_pton(AF_INET6, optarg, &c->ip6.gw)	&&
> +			if (inet_pton(AF_INET6, optarg, &c->ip6.gw)     &&
>  			    !IN6_IS_ADDR_UNSPECIFIED(&c->ip6.gw)	&&
>  			    !IN6_IS_ADDR_LOOPBACK(&c->ip6.gw))
>  				break;
>  
> -			if (IN4_IS_ADDR_UNSPECIFIED(&c->ip4.gw)		&&
> -			    inet_pton(AF_INET, optarg, &c->ip4.gw)	&&
> +			if (inet_pton(AF_INET, optarg, &c->ip4.gw)	&&
>  			    !IN4_IS_ADDR_UNSPECIFIED(&c->ip4.gw)	&&
>  			    !IN4_IS_ADDR_BROADCAST(&c->ip4.gw)		&&
>  			    !IN4_IS_ADDR_LOOPBACK(&c->ip4.gw))
> @@ -1558,16 +1511,12 @@ void conf(struct ctx *c, int argc, char **argv)
>  			die("Invalid gateway address: %s", optarg);
>  			break;
>  		case 'i':
> -			if (ifi4 || ifi6)
> -				die("Redundant interface: %s", optarg);
> -
>  			if (!(ifi4 = ifi6 = if_nametoindex(optarg)))
>  				die("Invalid interface name %s: %s", optarg,
>  				    strerror(errno));
>  			break;
>  		case 'o':
> -			if (IN6_IS_ADDR_UNSPECIFIED(&c->ip6.addr_out)	  &&
> -			    inet_pton(AF_INET6, optarg, &c->ip6.addr_out) &&
> +			if (inet_pton(AF_INET6, optarg, &c->ip6.addr_out) &&
>  			    !IN6_IS_ADDR_UNSPECIFIED(&c->ip6.addr_out)	  &&
>  			    !IN6_IS_ADDR_LOOPBACK(&c->ip6.addr_out)	  &&
>  			    !IN6_IS_ADDR_V4MAPPED(&c->ip6.addr_out)	  &&
> @@ -1575,8 +1524,7 @@ void conf(struct ctx *c, int argc, char **argv)
>  			    !IN6_IS_ADDR_MULTICAST(&c->ip6.addr_out))
>  				break;
>  
> -			if (IN4_IS_ADDR_UNSPECIFIED(&c->ip4.addr_out)	 &&
> -			    inet_pton(AF_INET, optarg, &c->ip4.addr_out) &&
> +			if (inet_pton(AF_INET, optarg, &c->ip4.addr_out) &&
>  			    !IN4_IS_ADDR_UNSPECIFIED(&c->ip4.addr_out)	 &&
>  			    !IN4_IS_ADDR_BROADCAST(&c->ip4.addr_out)	 &&
>  			    !IN4_IS_ADDR_MULTICAST(&c->ip4.addr_out))
> @@ -1587,18 +1535,23 @@ void conf(struct ctx *c, int argc, char **argv)
>  			break;
>  		case 'D':
>  			if (!strcmp(optarg, "none")) {
> -				if (c->no_dns)
> -					die("Redundant DNS options");
> +				c->no_dns = 1;
>  
> -				if (dns4 - c->ip4.dns || dns6 - c->ip6.dns)
> -					die("Conflicting DNS options");
> +				dns4 = &c->ip4.dns[0];
> +				memset(c->ip4.dns, 0, sizeof(c->ip4.dns));
> +				c->ip4.dns[0]    = (struct in_addr){ 0 };
> +				c->ip4.dns_match = (struct in_addr){ 0 };
> +				c->ip4.dns_host  = (struct in_addr){ 0 };
> +
> +				dns6 = &c->ip6.dns[0];
> +				memset(c->ip6.dns, 0, sizeof(c->ip6.dns));
> +				c->ip6.dns_match = (struct in6_addr){ 0 };
> +				c->ip6.dns_host  = (struct in6_addr){ 0 };
>  
> -				c->no_dns = 1;
>  				break;
>  			}
>  
> -			if (c->no_dns)
> -				die("Conflicting DNS options");
> +			c->no_dns = 0;
>  
>  			if (dns4 - &c->ip4.dns[0] < ARRAY_SIZE(c->ip4.dns) &&
>  			    inet_pton(AF_INET, optarg, &dns4_tmp)) {
> @@ -1616,18 +1569,14 @@ void conf(struct ctx *c, int argc, char **argv)
>  			break;
>  		case 'S':
>  			if (!strcmp(optarg, "none")) {
> -				if (c->no_dns_search)
> -					die("Redundant DNS search options");
> +				c->no_dns_search = 1;
>  
> -				if (dnss != c->dns_search)
> -					die("Conflicting DNS search options");
> +				memset(c->dns_search, 0, sizeof(c->dns_search));
>  
> -				c->no_dns_search = 1;
>  				break;
>  			}
>  
> -			if (c->no_dns_search)
> -				die("Conflicting DNS search options");
> +			c->no_dns_search = 0;
>  
>  			if (dnss - c->dns_search < ARRAY_SIZE(c->dns_search)) {
>  				ret = snprintf(dnss->n, sizeof(*c->dns_search),
> @@ -1643,17 +1592,16 @@ void conf(struct ctx *c, int argc, char **argv)
>  			break;
>  		case '4':
>  			v4_only = true;
> +			v6_only = false;
>  			break;
>  		case '6':
>  			v6_only = true;
> +			v4_only = false;
>  			break;
>  		case '1':
>  			if (c->mode == MODE_PASTA)
>  				die("--one-off is for passt mode only");
>  
> -			if (c->one_off)
> -				die("Redundant --one-off option");
> -
>  			c->one_off = true;
>  			break;
>  		case 't':
> @@ -1672,12 +1620,6 @@ void conf(struct ctx *c, int argc, char **argv)
>  		}
>  	} while (name != -1);
>  
> -	if (v4_only && v6_only)
> -		die("Options ipv4-only and ipv6-only are mutually exclusive");
> -
> -	if (*c->sock_path && c->fd_tap >= 0)
> -		die("Options --socket and --fd are mutually exclusive");
> -
>  	if (c->mode == MODE_PASTA && !c->pasta_conf_ns) {
>  		if (copy_routes_opt)
>  			die("--no-copy-routes needs --config-net");
> diff --git a/passt.1 b/passt.1
> index 7676fe3..7b9915b 100644
> --- a/passt.1
> +++ b/passt.1
> @@ -73,6 +73,9 @@ for performance reasons.
>  
>  .SH OPTIONS
>  
> +Unless otherwise noted below, \fBif conflicting or multiple options are given,
> +the last one takes effect.\fR
> +
>  .TP
>  .BR \-d ", " \-\-debug
>  Be verbose, don't log to the system logger.
> @@ -97,10 +100,21 @@ Log to standard error too.
>  Default is to log to the system logger only, if started from an interactive
>  terminal, and to both system logger and standard error otherwise.
>  
> +This option cannot be specified together with \fB--log-file\fR, because there
> +might be a reasonable expectation that messages are logged to standard error as
> +well as to a file, which is however not supported.
> +
>  .TP
>  .BR \-l ", " \-\-log-file " " \fIPATH\fR
>  Log to file \fIPATH\fR, not to standard error, and not to the system logger.
>  
> +This option cannot be specified together with \fB--stderr\fR, because there
> +might be a reasonable expectation that messages are logged to a file as well as
> +to standard error, which is however not supported.
> +
> +Specifying this option multiple times does \fInot\fR lead to multiple log files:
> +the last given option takes effect.
> +
>  .TP
>  .BR \-\-log-size " " \fISIZE\fR
>  Limit log file size to \fISIZE\fR bytes. When the log file is full, make room
> @@ -128,6 +142,9 @@ Show version and exit.
>  Capture tap-facing (that is, guest-side or namespace-side) network packets to
>  \fIfile\fR in \fBpcap\fR format.
>  
> +Specifying this option multiple times does \fInot\fR lead to multiple capture
> +files: the last given option takes effect.
> +
>  .TP
>  .BR \-P ", " \-\-pid " " \fIfile
>  Write own PID to \fIfile\fR once initialisation is done, before forking to

-- 
David Gibson (he or they)	| 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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