Re: [PATCH v6 05/13] conf: Allow multiple -a/--address options per address family

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

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On Sat, Mar 21, 2026 at 08:43:25PM -0400, Jon Maloy wrote:
> Allow specifying multiple addresses per family with -a/--address.
> The first address of each family is used for DHCP/DHCPv6 assignment.
> 
> Signed-off-by: Jon Maloy <jmaloy@redhat.com>
> 
> ---
> v2: - Adapted to previous code changes
> v3: - Adapted to single-array strategy
>     - Changes according to feedback from S. Brivio and G Gibson.
> v4: - Stripped down and adapted after feedback from David G.
> v6: - Adapted to previous changes in series
>     - Removed the "one address" limitation for -n option
> ---
>  conf.c  |  7 ++++---
>  fwd.c   |  7 ++-----
>  pasta.c | 17 ++++++++++-------
>  3 files changed, 16 insertions(+), 15 deletions(-)
> 
> diff --git a/conf.c b/conf.c
> index 8f02494..95f09cb 100644
> --- a/conf.c
> +++ b/conf.c
> @@ -935,9 +935,11 @@ static void usage(const char *name, FILE *f, int status)
>  		"    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[/PREFIXLEN]\n"
> -		"    can be specified zero to two times (for IPv4 and IPv6)\n"
> +		"    can be specified up to a maximum of %d times\n"
>  		"    default: use addresses from interface with default route\n"
> -		"  -n, --netmask MASK	Assign IPv4 MASK, dot-decimal or bits\n"
> +		"  -n, --netmask MASK	Assign IPv4 MASK, dot-decimal or bits\n",
> +		MAX_GUEST_ADDRS);
> +	FPRINTF(f,
>  		"    default: netmask from matching address on the host\n"
>  		"  -M, --mac-addr ADDR	Use source MAC address ADDR\n"
>  		"    default: 9a:55:9a:55:9a:55 (locally administered)\n"
> @@ -1891,7 +1893,6 @@ void conf(struct ctx *c, int argc, char **argv)
>  			    IN6_IS_ADDR_V4COMPAT(&addr.a6))
>  				die("Invalid address: %s", optarg);
>  
> -			/* Legacy behaviour: replace existing address if any */
>  			fwd_set_addr(c, &addr, CONF_ADDR_USER, prefix_len);
>  			if (inany_v4(&addr))
>  				c->ip4.no_copy_addrs = true;
> diff --git a/fwd.c b/fwd.c
> index 695b5a5..2853c0e 100644
> --- a/fwd.c
> +++ b/fwd.c
> @@ -250,14 +250,12 @@ void fwd_neigh_table_init(const struct ctx *c)
>  }
>  
>  /**
> - * fwd_set_addr() - Add or update an address in the unified address array
> + * fwd_set_addr() - Update address entry, adding one if needed
>   * @c:		Execution context
>   * @addr:	Address to add (IPv4-mapped or IPv6)
>   * @flags:	CONF_ADDR_* flags for this address
>   * @prefix_len:	Prefix length in IPv6/mapped format, 0-128
>   *
> - * Find the first existing entry of the same address family and
> - * overwrite it, or create a new one if none exists
>   */
>  void fwd_set_addr(struct ctx *c, const union inany_addr *addr,
>  		  uint8_t flags, int prefix_len)
> @@ -266,8 +264,7 @@ void fwd_set_addr(struct ctx *c, const union inany_addr *addr,
>  
>  	for (int i = 0; i < c->addr_count; i++) {
>  		a = &c->addrs[i];
> -		if ((inany_v4(addr) && inany_v4(&a->addr)) ||
> -		    (!inany_v4(addr) && !inany_v4(&a->addr)))
> +		if (inany_equals(addr, &a->addr))
>  			goto found;
>  	}
>  
> diff --git a/pasta.c b/pasta.c
> index e88a893..6307c65 100644
> --- a/pasta.c
> +++ b/pasta.c
> @@ -342,12 +342,14 @@ void pasta_ns_conf(struct ctx *c)
>  
>  		if (c->ifi4) {
>  			if (c->ip4.no_copy_addrs) {
> -				a = fwd_get_addr(c, AF_INET, 0, 0);
> -				if (a)
> +				for_each_addr(a, c, AF_INET) {

I think this will work out cleaner if you have a single loop for all
addresses, then do the v4 vs. v6 conditionals in the body.

>  					rc = nl_addr_set(nl_sock_ns,
>  							 c->pasta_ifi, AF_INET,
>  							 inany_v4(&a->addr),
> -							 a->prefix_len - 96);
> +							 inany_prefix_len(a));
> +					if (rc < 0)
> +						break;
> +				}
>  			} else {
>  				rc = nl_addr_dup(nl_sock, c->ifi4,
>  						 nl_sock_ns, c->pasta_ifi,
> @@ -400,13 +402,14 @@ ipv4_done:
>  					  0, IFF_NOARP);
>  
>  			if (c->ip6.no_copy_addrs) {
> -				a = fwd_get_addr(c, AF_INET6, 0, 0);
> -				if (a)
> +				for_each_addr(a, c, AF_INET6) {
>  					rc = nl_addr_set(nl_sock_ns,
>  							 c->pasta_ifi,
> -							 AF_INET6,
> -							 &a->addr.a6,
> +							 AF_INET6, &a->addr.a6,
>  							 a->prefix_len);
> +					if (rc < 0)
> +						break;
> +				}
>  			} else {
>  				rc = nl_addr_dup(nl_sock, c->ifi6,
>  						 nl_sock_ns, c->pasta_ifi,
> -- 
> 2.52.0
> 

-- 
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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