Re: [PATCH v6 01/13] conf: use a single buffer for print formatting in conf_print()

On Sat, Mar 21, 2026 at 08:43:21PM -0400, Jon Maloy wrote:

The function conf_print() uses three different buffers as target for address print formatting. This is unnecessary, as a single buffer of length INET6_ADDRSTRLEN has sufficient space for all address types, IPv4, IPv6 and MAC. There is no risk for conflicts, since all formatting is followed by an immediate info() printout.

To make our life easier in the following commits, we do this simplification here.

Signed-off-by: Jon Maloy --- conf.c | 35 ++++++++++++++++++----------------- 1 file changed, 18 insertions(+), 17 deletions(-)

diff --git a/conf.c b/conf.c index dafac46..9bcd9de 100644 --- a/conf.c +++ b/conf.c @@ -1136,11 +1136,12 @@ enum passt_modes conf_mode(int argc, char *argv[]) */ static void conf_print(const struct ctx *c) { - char buf4[INET_ADDRSTRLEN], buf6[INET6_ADDRSTRLEN]; - char bufmac[ETH_ADDRSTRLEN], ifn[IFNAMSIZ]; + char buf[INET6_ADDRSTRLEN];

INANY_ADDRSTRLEN is already defined to be the max of INET_ADDRSTRLEN and INET6_ADDRSTRLEN.

int i;

if (c->ifi4 > 0 || c->ifi6 > 0) { + char ifn[IFNAMSIZ]; + info("Template interface: %s%s%s%s%s", c->ifi4 > 0 ? if_indextoname(c->ifi4, ifn) : "", c->ifi4 > 0 ? " (IPv4)" : "", @@ -1162,24 +1163,24 @@ static void conf_print(const struct ctx *c) !IN6_IS_ADDR_UNSPECIFIED(&c->ip6.addr_out)) { info("Outbound address: %s%s%s", IN4_IS_ADDR_UNSPECIFIED(&c->ip4.addr_out) ? "" : - inet_ntop(AF_INET, &c->ip4.addr_out, buf4, sizeof(buf4)), + inet_ntop(AF_INET, &c->ip4.addr_out, buf, sizeof(buf)), (!IN4_IS_ADDR_UNSPECIFIED(&c->ip4.addr_out) && !IN6_IS_ADDR_UNSPECIFIED(&c->ip6.addr_out)) ? ", " : "", IN6_IS_ADDR_UNSPECIFIED(&c->ip6.addr_out) ? "" : - inet_ntop(AF_INET6, &c->ip6.addr_out, buf6, sizeof(buf6))); + inet_ntop(AF_INET6, &c->ip6.addr_out, buf, sizeof(buf)));

This one won't work: you're using the same buffer twice for the same print. The buffer will be overwritten by the second inet_ntop() before the results from the first one are printed.

}

if (c->mode == MODE_PASTA && !c->splice_only) info("Namespace interface: %s", c->pasta_ifn);

info("MAC:"); - info(" host: %s", eth_ntop(c->our_tap_mac, bufmac, sizeof(bufmac))); + info(" host: %s", eth_ntop(c->our_tap_mac, buf, sizeof(buf)));

if (c->ifi4) { if (!IN4_IS_ADDR_UNSPECIFIED(&c->ip4.map_host_loopback)) info(" NAT to host 127.0.0.1: %s", inet_ntop(AF_INET, &c->ip4.map_host_loopback, - buf4, sizeof(buf4))); + buf, sizeof(buf)));

if (!c->no_dhcp) { uint32_t mask; @@ -1188,12 +1189,12 @@ static void conf_print(const struct ctx *c)

info("DHCP:"); info(" assign: %s", - inet_ntop(AF_INET, &c->ip4.addr, buf4, sizeof(buf4))); + inet_ntop(AF_INET, &c->ip4.addr, buf, sizeof(buf))); info(" mask: %s", - inet_ntop(AF_INET, &mask, buf4, sizeof(buf4))); + inet_ntop(AF_INET, &mask, buf, sizeof(buf))); info(" router: %s", inet_ntop(AF_INET, &c->ip4.guest_gw, - buf4, sizeof(buf4))); + buf, sizeof(buf))); }

for (i = 0; i < ARRAY_SIZE(c->ip4.dns); i++) { @@ -1201,8 +1202,8 @@ static void conf_print(const struct ctx *c) break; if (!i) info("DNS:"); - inet_ntop(AF_INET, &c->ip4.dns[i], buf4, sizeof(buf4)); - info(" %s", buf4); + inet_ntop(AF_INET, &c->ip4.dns[i], buf, sizeof(buf)); + info(" %s", buf); }

for (i = 0; *c->dns_search[i].n; i++) { @@ -1216,7 +1217,7 @@ static void conf_print(const struct ctx *c) if (!IN6_IS_ADDR_UNSPECIFIED(&c->ip6.map_host_loopback)) info(" NAT to host ::1: %s", inet_ntop(AF_INET6, &c->ip6.map_host_loopback, - buf6, sizeof(buf6))); + buf, sizeof(buf)));

if (!c->no_ndp && !c->no_dhcpv6) info("NDP/DHCPv6:"); @@ -1228,12 +1229,12 @@ static void conf_print(const struct ctx *c) goto dns6;

info(" assign: %s", - inet_ntop(AF_INET6, &c->ip6.addr, buf6, sizeof(buf6))); + inet_ntop(AF_INET6, &c->ip6.addr, buf, sizeof(buf))); info(" router: %s", - inet_ntop(AF_INET6, &c->ip6.guest_gw, buf6, sizeof(buf6))); + inet_ntop(AF_INET6, &c->ip6.guest_gw, buf, sizeof(buf))); info(" our link-local: %s", inet_ntop(AF_INET6, &c->ip6.our_tap_ll, - buf6, sizeof(buf6))); + buf, sizeof(buf)));

dns6: for (i = 0; i < ARRAY_SIZE(c->ip6.dns); i++) { @@ -1241,8 +1242,8 @@ dns6: break; if (!i) info("DNS:"); - inet_ntop(AF_INET6, &c->ip6.dns[i], buf6, sizeof(buf6)); - info(" %s", buf6); + inet_ntop(AF_INET6, &c->ip6.dns[i], buf, sizeof(buf)); + info(" %s", buf); }

for (i = 0; *c->dns_search[i].n; i++) { -- 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