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

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

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On Tue, Jun 18, 2024 at 06:17:23PM +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.
> 
> Finally, somebody took care of this on Podman side at:
>   https://github.com/containers/common/pull/2052
> 
> but still, we'll probably have similar cases, or older versions of
> Podman around, etc.
> 
> 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.

I tend to agree.

> 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.
> 
> Suggested-by: Paul Holzinger <pholzing@redhat.com>
> Suggested-by: David Gibson <david@gibson.dropbear.id.au>
> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

[snip]
> +		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;

I would suggest leaving this one as is for now.  I think the least
surprising behaviour for -e and -l together would be to log to both
stderr and the file.  They're not inherently contradictory, it's just
because of an implementation limitation.  Theferore, in this case, I
think it's best to give an error rather than behaving in a surprising
way.  Later on we can implement being able to log to both at once.

>  		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;

Same here, of course.


>  			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);

I'm a little bit dubious about this one too.  In terms of pure
semantics, then yes, overriding makes sense.  But -F specifically
requires the caller to have set up fds in specific slots, so it's
pretty hard to see a real situation where overriding this would make
sense.

> @@ -1460,12 +1421,9 @@ void conf(struct ctx *c, int argc, char **argv)
>  				die("Invalid --fd: %s", optarg);
>  
>  			c->one_off = true;
> -
> +			*c->sock_path = 0;

This makes sense, although we weren't actually giving an error for
that case previously.

>  			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)
> @@ -1473,18 +1431,12 @@ void conf(struct ctx *c, int argc, char **argv)
>  
>  			break;
>  		case 'p':
> -			if (*c->pcap)
> -				die("Multiple --pcap options given");
> -

Again, I'm unsure about this one, since I think the least surprising
behaviour would be to write to _all_ the listed pcap files.

>  			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))
> @@ -1492,9 +1444,6 @@ 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);
>  
> @@ -1544,14 +1493,12 @@ 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))
> @@ -1560,15 +1507,11 @@ 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_perror("Invalid interface name %s", optarg);
>  			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)	  &&
> @@ -1576,8 +1519,7 @@ 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))
> @@ -1588,18 +1530,23 @@ 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)) {
> @@ -1617,18 +1564,14 @@ 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),
> @@ -1644,17 +1587,16 @@ 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':
> @@ -1673,12 +1615,6 @@ 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");

This could now be an ASSERT() instead of an error message.

> -	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 31e528e..6dfa670 100644
> --- a/passt.1
> +++ b/passt.1
> @@ -73,6 +73,8 @@ for performance reasons.
>  
>  .SH OPTIONS
>  
> +\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.

-- 
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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