Re: [PATCH v5 15/18] pesto: Read current ruleset from passt/pasta and optionally display it

[Jon Maloy <jmaloy@redhat.com>]

On 2026-04-21 02:25, David Gibson wrote:
> Implement serialisation of our current forwarding rules in conf.c,
> deserialising it to display in the pesto client.  Doing this requires
> adding ip.c, inany.c, bitmap.c, lineread.c and fwd_rule.c to the pesto
> build.  With previous preparations that now requires only a trivial change
[...]

> +
> +
> +/**
> + * fwd_rule_read() - Read serialised rule from an fd
> + * @fd:		fd to serialise to
> + * @rule:	Buffer to store rule into
> + *
> + * Return: 0 on success, -1 on error (with errno set)
> + */
> +int fwd_rule_read(int fd, struct fwd_rule *rule)
> +{
> +	if (read_all_buf(fd, rule, sizeof(*rule)))
> +		return -1;
> +
> +	/* Byteswap for host */
> +	rule->first = ntohs(rule->first);
> +	rule->last = ntohs(rule->last);
> +	rule->to = htons(rule->to);
Or ntohs() ?

/jon
> +
> +	return 0;
> +}
> +
> +/**
> + * fwd_rule_write() - Serialise rule to an fd
> + * @fd:		fd to serialise to
> + * @rule:	Rule to send
> + *
> + * Return: 0 on success, -1 on error (with errno set)
> + */
> +int fwd_rule_write(int fd, const struct fwd_rule *rule)
> +{
> +	struct fwd_rule tmp = *rule;
> +
> +	/* Byteswap for transport */
> +	tmp.first = htons(tmp.first);
> +	tmp.last = htons(tmp.last);
> +	tmp.to = htons(tmp.to);
> +
> +	return write_all_buf(fd, &tmp, sizeof(tmp));
> +}
> diff --git a/fwd_rule.h b/fwd_rule.h
> index f51f1b4b..330d49eb 100644
> --- a/fwd_rule.h
> +++ b/fwd_rule.h
> @@ -29,6 +29,8 @@
>   #define FWD_CAP_UDP		BIT(3)
>   #define FWD_CAP_SCAN		BIT(4)
>   #define FWD_CAP_IFNAME		BIT(5)
> +#define FWD_CAP_ALL		(FWD_CAP_IPV4 | FWD_CAP_IPV6 | FWD_CAP_TCP | \
> +				 FWD_CAP_UDP | FWD_CAP_SCAN | FWD_CAP_IFNAME)
>   
>   /**
>    * struct fwd_rule - Forwarding rule governing a range of ports
> @@ -99,6 +101,8 @@ void fwd_probe_ephemeral(void);
>   const union inany_addr *fwd_rule_addr(const struct fwd_rule *rule);
>   const char *fwd_rule_fmt(const struct fwd_rule *rule, char *dst, size_t size);
>   void fwd_rule_parse(char optname, const char *optarg, struct fwd_table *fwd);
> +int fwd_rule_read(int fd, struct fwd_rule *rule);
> +int fwd_rule_write(int fd, const struct fwd_rule *rule);
>   
>   /**
>    * fwd_rules_dump() - Dump forwarding rules
> diff --git a/lineread.c b/lineread.c
> index b9ceae10..a4269a66 100644
> --- a/lineread.c
> +++ b/lineread.c
> @@ -19,8 +19,8 @@
>   #include <stdbool.h>
>   #include <unistd.h>
>   
> +#include "common.h"
>   #include "lineread.h"
> -#include "util.h"
>   
>   /**
>    * lineread_init() - Prepare for line by line file reading without allocation
> diff --git a/pesto.c b/pesto.c
> index 3e34bbac..35a4d559 100644
> --- a/pesto.c
> +++ b/pesto.c
> @@ -34,6 +34,7 @@
>   #include "common.h"
>   #include "seccomp_pesto.h"
>   #include "serialise.h"
> +#include "fwd_rule.h"
>   #include "pesto.h"
>   #include "log.h"
>   
> @@ -66,6 +67,7 @@ static void usage(const char *name, FILE *f, int status)
>   struct pif_configuration {
>   	uint8_t pif;
>   	char name[PIF_NAME_SIZE];
> +	struct fwd_table fwd;
>   };
>   
>   struct configuration {
> @@ -123,6 +125,7 @@ static bool read_pif_conf(int fd, struct configuration *conf)
>   	struct pif_configuration *pc;
>   	struct pesto_pif_info info;
>   	uint8_t pif;
> +	unsigned i;
>   
>   	if (read_u8(fd, &pif) < 0)
>   		die("Error reading from control socket");
> @@ -149,8 +152,17 @@ static bool read_pif_conf(int fd, struct configuration *conf)
>   	static_assert(sizeof(info.name) == sizeof(pc->name),
>   		      "Mismatching pif name lengths");
>   	memcpy(pc->name, info.name, sizeof(pc->name));
> -
> -	debug("PIF %"PRIu8": %s", pc->pif, pc->name);
> +	pc->fwd.caps = ntohl(info.caps);
> +	pc->fwd.count = ntohl(info.count);
> +
> +	debug("PIF %"PRIu8": %s, %"PRIu32" rules, capabilities 0x%"PRIx32
> +	      ":%s%s%s%s%s%s", pc->pif, pc->name, pc->fwd.count, pc->fwd.caps,
> +	      pc->fwd.caps & FWD_CAP_IPV4 ? " IPv4" : "",
> +	      pc->fwd.caps & FWD_CAP_IPV6 ? " IPv6" : "",
> +	      pc->fwd.caps & FWD_CAP_TCP ? " TCP" : "",
> +	      pc->fwd.caps & FWD_CAP_UDP ? " UDP" : "",
> +	      pc->fwd.caps & FWD_CAP_SCAN ? " scan" : "",
> +	      pc->fwd.caps & FWD_CAP_IFNAME ? " ifname" : "");
>   
>   	/* O(n^2), but n is bounded by MAX_PIFS */
>   	if (pif_conf_by_num(conf, pc->pif))
> @@ -160,6 +172,18 @@ static bool read_pif_conf(int fd, struct configuration *conf)
>   	if (pif_conf_by_name(conf, pc->name))
>   		die("Received duplicate interface name");
>   
> +	/* NOTE: We read the fwd rules directly into fwd.rules, rather than
> +	 * using fwd_rule_add().  This means we can read and display rules even
> +	 * if something has gone wrong (in pesto or passt) and we get rules that
> +	 * fwd_rule_add() would reject.  It does have the side effect that we
> +	 * never assign socket space for the fwd rules, but we don't need that
> +	 * within pesto.
> +	 */
> +	for (i = 0; i < pc->fwd.count; i++) {
> +		if (fwd_rule_read(fd, &pc->fwd.rules[i]) < 0)
> +			die("Error reading from control socket");
> +	}
> +
>   	conf->npifs++;
>   	return true;
>   }
> @@ -175,7 +199,8 @@ static void show_conf(const struct configuration *conf)
>   	for (i = 0; i < conf->npifs; i++) {
>   		const struct pif_configuration *pc = &conf->pif[i];
>   		printf("  %s\n", pc->name);
> -		printf("    TBD\n");
> +		fwd_rules_dump(printf, pc->fwd.rules, pc->fwd.count,
> +			       "    ", "\n");
>   	}
>   }
>   
> @@ -288,6 +313,12 @@ int main(int argc, char **argv)
>   		    ntohl(hello.pif_name_size), PIF_NAME_SIZE);
>   	}
>   
> +	if (ntohl(hello.ifnamsiz) != IFNAMSIZ) {
> +		die("Server has unexpected IFNAMSIZ (%"
> +		    PRIu32" not %"PRIu32"\n",
> +		    ntohl(hello.ifnamsiz), IFNAMSIZ);
> +	}
> +	
>   	while (read_pif_conf(s, &conf))
>   		;
>   
> diff --git a/pesto.h b/pesto.h
> index ac4c2b58..8f6bbf65 100644
> --- a/pesto.h
> +++ b/pesto.h
> @@ -26,11 +26,13 @@
>    * @magic:		PESTO_SERVER_MAGIC
>    * @version:		Version number
>    * @pif_name_size:	Server's value for PIF_NAME_SIZE
> + * @ifnamsiz:		Server's value for IFNAMSIZ
>    */
>   struct pesto_hello {
>   	char magic[8];
>   	uint32_t version;
>   	uint32_t pif_name_size;
> +	uint32_t ifnamsiz;
>   } __attribute__ ((__packed__));
>   
>   static_assert(sizeof(PESTO_SERVER_MAGIC)
> @@ -41,9 +43,13 @@ static_assert(sizeof(PESTO_SERVER_MAGIC)
>    * struct pesto_pif_info - Message with basic metadata about a pif
>    * @resv_:	Alignment gap (must be 0)
>    * @name:	Name (\0 terminated)
> + * @caps:	Forwarding capabilities for this pif
> + * @count:	Number of forwarding rules for this pif
>    */
>   struct pesto_pif_info {
>   	char name[PIF_NAME_SIZE];
> +	uint32_t caps;
> +	uint32_t count;
>   } __attribute__ ((__packed__));
>   
>   #endif /* PESTO_H */