Re: [PATCH 10/12] conf: Use new parsing tools to handle -a option

On Wed, Jul 01, 2026 at 02:07:50AM +0200, Stefano Brivio wrote:

On Fri, 26 Jun 2026 17:10:01 +1000 David Gibson wrote:

...

The -a command line option can take either an address prefix, or a bare address. Current parsing of this is pretty awkward, using the special purpose helper inany_prefix_pton(). With the new incremental parsing helpers this can be done more naturally. Rework it to use them.

This does requiring extending parse_inany() to parse_inany_() which also reports the format of the address as parse, as opposed to the family of the resulting address. This is so that ::ffff:192.0.1.1/112 will be correctly interpreted the same as 192.0.1.1/16, rather than the nonsensical 192.0.0.1/112.

By the way, as far as I know, ::ffff:192.0.1.1/112 is not a valid address, because IPv4-mapped addresses must always have /96 as prefix length (see RFC 6890, Table 20).

AFAICT the /96 there is just indicating the size of the v4-mapped block, not saying you can't have longer prefixes within that block.

RFC 6052 adds some madness (e.g. 2001:db8:122:344::192.0.2.33 from Table 1) on top, but as far as I understand you can't use that for prefixes.

...

Cc: Jon Maloy

Signed-off-by: David Gibson --- Makefile | 1 - conf.c | 63 +++++++++++++++++++++++++++++++++++--------------------- inany.c | 50 -------------------------------------------- inany.h | 2 -- parse.c | 17 ++++++++++++--- parse.h | 5 ++++- 6 files changed, 58 insertions(+), 80 deletions(-)

diff --git a/Makefile b/Makefile index e2b22ddf..5757aeff 100644 --- a/Makefile +++ b/Makefile @@ -223,7 +223,6 @@ passt-repair.cppcheck: $(PASST_REPAIR_SRCS) $(PASST_REPAIR_HEADERS) seccomp_repa pesto.cppcheck: BASE_CPPFLAGS += -DPESTO pesto.cppcheck: CPPCHECK_FLAGS += --suppress=unusedFunction:bitmap.c pesto.cppcheck: CPPCHECK_FLAGS += --suppress=unusedFunction:inany.h -pesto.cppcheck: CPPCHECK_FLAGS += --suppress=unusedFunction:inany.c pesto.cppcheck: CPPCHECK_FLAGS += --suppress=unusedFunction:ip.h pesto.cppcheck: CPPCHECK_FLAGS += --suppress=unusedFunction:serialise.c pesto.cppcheck: CPPCHECK_FLAGS += --suppress=staticFunction:fwd_rule.c diff --git a/conf.c b/conf.c index 3614776c..ff7ca5c7 100644 --- a/conf.c +++ b/conf.c @@ -1176,43 +1176,60 @@ int conf_tap_fd(const char *arg) */ static bool conf_addr(struct ctx *c, char *arg, uint8_t opt_n) { + unsigned long prefix_len; + const struct in_addr *a4; union inany_addr addr; + sa_family_t parseaf;

I think parse_af would be more readable (and also more consistent with e.g. prefix_len).

Sure.

...

const char *p = arg; - uint8_t prefix_len; bool is_prefix;

- is_prefix = inany_prefix_pton(arg, &addr, &prefix_len); - - if (is_prefix && opt_n) - die("Redundant prefix length specification"); - - if (!is_prefix && - !(parse_inany(&p, &addr) && parse_eoi(p))) - die("Invalid address: %s", arg); - - if (opt_n && inany_v4(&addr)) - prefix_len = opt_n; - else if (!is_prefix) - prefix_len = inany_default_prefix_len(&addr); + if (!parse_inany_(&p, &addr, &parseaf))

...just call it af? It doesn't matter so much in the following code where that comes from. Starting from here, we know it's the address family we're using.

Eh.. I don't like that, because just "af" suggests it's the address family of the address itself. That's not the case - it's very specifically the address family of the *string* not the resulting address.

...

+ goto bad; + a4 = inany_v4(&addr); + + if ((is_prefix = parse_literal(&p, "/"))) {

The current return convention makes more sense here, but I wouldn't find:

is_prefix = !parse_literal(&p, "/")

outrageous, either.

...

+ /* Prefix length included in -a option */ + if (!parse_unsigned(&p, 10, &prefix_len)) + goto bad; + if (opt_n) + die("Redundant prefix length specification"); + if (parseaf == AF_INET) { + if (prefix_len > 32) + goto bad_prefix; + prefix_len += 96; + } else if (prefix_len > 128) { + goto bad_prefix; + } + } else { + /* Get prefix length from elsewhere */ + if (opt_n && a4) + prefix_len = opt_n; + else + prefix_len = inany_default_prefix_len(&addr); + }

- if (inany_is_unspecified(&addr) || inany_is_multicast(&addr) || - inany_is_loopback(&addr) || IN6_IS_ADDR_V4COMPAT(&addr.a6)) - die("Invalid address: %s", arg); + if (!parse_eoi(p) ||

Note: with *p instead of !parse_eoi(), this would fit on one line.

...

+ !inany_is_unicast(&addr) || + inany_is_loopback(&addr)) + goto bad;

- if (inany_v4(&addr)) { - c->ip4.addr = *inany_v4(&addr); + if (a4) { + c->ip4.addr = *a4; c->ip4.prefix_len = prefix_len - 96; c->ip4.addr_fixed = true; - if (c->mode == MODE_PASTA)

Why does this (and the same condition just below) go away here? I mean, it's not fundamental in any case, but changing it here makes it look like it has something to do with this change (and I guess it's not the case).

Good point, that's an unrelated change. I split it into its own patch.

...

- c->ip4.no_copy_addrs = true; + c->ip4.no_copy_addrs = true; } else { c->ip6.addr = addr.a6; c->ip6.addr_fixed = true; - if (c->mode == MODE_PASTA) - c->ip6.no_copy_addrs = true; + c->ip6.no_copy_addrs = true; }

return is_prefix; + +bad_prefix: + die("Invalid prefix length: %s", arg); +bad: + die("Invalid guest address: %s", arg); }

/** diff --git a/inany.c b/inany.c index 154f08b5..120c9387 100644 --- a/inany.c +++ b/inany.c @@ -70,53 +70,3 @@ const char *inany_ntop(const union inany_addr *src, char *dst, socklen_t size)

return inet_ntop(AF_INET6, &src->a6, dst, size); } - -/** - * inany_prefix_pton() - Parse an IPv[46] address with prefix length - * @src: IPv[46] address and prefix length string in CIDR format - * @dst: Output buffer, filled with parsed address - * @prefix_len: Prefix length, to be filled in IPv6 format - * - * Return: 1 on success, 0 if no parseable address or prefix is found - */ -int inany_prefix_pton(const char *src, union inany_addr *dst, - uint8_t *prefix_len) -{ - char astr[INANY_ADDRSTRLEN] = { 0 }; - size_t alen = strcspn(src, "/"); - const char *pstr = &src[alen + 1]; - const char *p = astr; - unsigned long plen; - char *end; - - if (alen >= INANY_ADDRSTRLEN) - return 0; - - if (src[alen] != '/') - return 0; - - strncpy(astr, src, alen); - - /* Read prefix length */ - errno = 0; - plen = strtoul(pstr, &end, 10); - if (errno || *end || plen > 128) - return 0; - - /* Read address */ - if (inet_pton(AF_INET6, astr, dst)) { - if (inany_v4(dst) && plen < 96) - return 0; - *prefix_len = plen; - return 1; - } - - if (parse_inany(&p, dst) && parse_eoi(p)) { - if (plen > 32) - return 0; - *prefix_len = plen + 96; - return 1; - } - - return 0; -} diff --git a/inany.h b/inany.h index 93d98368..5b176ccf 100644 --- a/inany.h +++ b/inany.h @@ -303,7 +303,5 @@ static inline int inany_from_sockaddr(union inany_addr *dst, in_port_t *port,

bool inany_matches(const union inany_addr *a, const union inany_addr *b); const char *inany_ntop(const union inany_addr *src, char *dst, socklen_t size); -int inany_prefix_pton(const char *src, union inany_addr *dst, - uint8_t *prefix_len);

#endif /* INANY_H */ diff --git a/parse.c b/parse.c index 0349c5dc..3e0dbd45 100644 --- a/parse.c +++ b/parse.c @@ -184,18 +184,29 @@ static bool parse_ipv6(const char **cursor, struct in6_addr *abuf) }

/** - * parse_inany() - Parse an IPv4 or IPv6 address from a string + * parse_inany_() - Parse an IPv4 or IPv6 address from a string * @addr: On success, updated with parsed address + * @parseaf: On success, updated with the format of the parsed address + * + * @parseaf is updated to reflect the string format, not the final address + * family. So "::ffff:192.0.1.1", will set @parseaf to AF_INET6, despite being + * a IPv4-mapped address. */ -bool parse_inany(const char **cursor, union inany_addr *addr) +bool parse_inany_(const char **cursor, union inany_addr *addr, + sa_family_t *parseaf) { struct in_addr a4;

- if (parse_ipv6(cursor, &addr->a6)) + if (parse_ipv6(cursor, &addr->a6)) { + if (parseaf) + *parseaf = AF_INET6; return true; + }

if (parse_ipv4(cursor, &a4)) { *addr = inany_from_v4(a4); + if (parseaf) + *parseaf = AF_INET; return true; }

diff --git a/parse.h b/parse.h index 2820a065..08b038cf 100644 --- a/parse.h +++ b/parse.h @@ -27,6 +27,9 @@ bool parse_eoi(const char *cursor); bool parse_unsigned(const char **cursor, int base, unsigned long *valp); bool parse_port_range(const char **cursor, struct port_range *range); bool parse_ipv4(const char **cursor, struct in_addr *abuf); -bool parse_inany(const char **cursor, union inany_addr *addr); +bool parse_inany_(const char **cursor, union inany_addr *addr, + sa_family_t *parseaf); + +#define parse_inany(cursor, addr) parse_inany_((cursor), (addr), NULL)

#endif /* _PARSE_H */

-- Stefano

-- 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