On Fri, 16 Aug 2024 15:40:00 +1000 David Gibson <david(a)gibson.dropbear.id.au> wrote:The @gw fields in the ip4_ctx and ip6_ctx give the (host's) default gateway. We use this for two quite distinct things: advertising the gateway that the guest should use (via DHCP, NDP and/or --config-net) and for a limited form of NAT. So that the guest can access services on the host, we map the gateway address within the guest to the loopback address on the host. Using the gateway address for this isn't necessarily the best choice for this purpose, certainly not for all circumstances. So, start off by splitting the notion of these into two different values: @guest_gw which is the gateway address the guest should use and @nat_host_loopback, which is the guest visible address to remap to the host's loopback. Usually nat_host_loopback will have the same value as guest_gw. However when --no-map-gw is specified we leave them unspecified instead. This means when we use nat_host_loopback, we don't need to separately check c->no_map_gw to see if it's relevant. Signed-off-by: David Gibson <david(a)gibson.dropbear.id.au> --- conf.c | 60 +++++++++++++++++++++++++++++---------------------------- dhcp.c | 10 ++++++---- fwd.c | 4 ++-- passt.h | 16 +++++++++------ pasta.c | 6 ++++-- 5 files changed, 53 insertions(+), 43 deletions(-) diff --git a/conf.c b/conf.c index b1c58d5b..26373584 100644 --- a/conf.c +++ b/conf.c @@ -410,12 +410,12 @@ static void add_dns_resolv(struct ctx *c, const char *nameserver, * redirect */ if (IN4_IS_ADDR_LOOPBACK(&ns4)) { - if (c->no_map_gw) + if (IN4_IS_ADDR_UNSPECIFIED(&c->ip4.nat_host_loopback))If you change the command-line option name to use "map", it would be good to also change these names. -- Stefano