On Wed, Nov 09, 2022 at 06:38:08PM +0100, Stefano Brivio wrote:

If we disable a given IP version automatically (no corresponding default route on host) or administratively (--ipv4-only or --ipv6-only options), we don't initialise related buffers and services (DHCP for IPv4, NDP and DHCPv6 for IPv6). The "tap" handlers will also ignore packets with a disabled IP version.

However, in commit 3c6ae625101a ("conf, tcp, udp: Allow address specification for forwarded ports") I happily changed socket initialisation functions to take AF_UNSPEC meaning "any enabled IP version", but I forgot to add checks back for the "enabled" part.

Reported by Paul: on a host without default IPv6 route, but IPv6 enabled, connect, using IPv6, to a port handled by pasta, which tries to send data to a tap device without initialised buffers for that IP version and exits because the resulting write() fails.

Simpler way to reproduce: pasta -6 and inbound IPv4 connection, or pasta -4 and inbound IPv6 connection.

Reported-by: Paul Holzinger Fixes: 3c6ae625101a ("conf, tcp, udp: Allow address specification for forwarded ports") Signed-off-by: Stefano Brivio

Heh, I also noticed this while working on the dual stack socket stuff, but didn't get around to fixing it yet. Reviewed-by: David Gibson

--- tcp.c | 4 ++-- udp.c | 4 ++-- 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/tcp.c b/tcp.c index 713248f..d043123 100644 --- a/tcp.c +++ b/tcp.c @@ -3213,9 +3213,9 @@ static void tcp_sock_init6(const struct ctx *c, int ns, void tcp_sock_init(const struct ctx *c, int ns, sa_family_t af, const void *addr, const char *ifname, in_port_t port) { - if (af == AF_INET || af == AF_UNSPEC) + if ((af == AF_INET || af == AF_UNSPEC) && c->ifi4) tcp_sock_init4(c, ns, addr, ifname, port); - if (af == AF_INET6 || af == AF_UNSPEC) + if ((af == AF_INET6 || af == AF_UNSPEC) && c->ifi6) tcp_sock_init6(c, ns, addr, ifname, port); }

diff --git a/udp.c b/udp.c index 42a17a7..ff7f993 100644 --- a/udp.c +++ b/udp.c @@ -1129,7 +1129,7 @@ void udp_sock_init(const struct ctx *c, int ns, sa_family_t af, c->udp.fwd_in.f.delta[port]); }

- if (af == AF_INET || af == AF_UNSPEC) { + if ((af == AF_INET || af == AF_UNSPEC) && c->ifi4) { if (!addr && c->mode == MODE_PASTA) bind_addr = &c->ip4.addr; else @@ -1162,7 +1162,7 @@ void udp_sock_init(const struct ctx *c, int ns, sa_family_t af, } }

- if (af == AF_INET6 || af == AF_UNSPEC) { + if ((af == AF_INET6 || af == AF_UNSPEC) && c->ifi6) { if (!addr && c->mode == MODE_PASTA) bind_addr = &c->ip6.addr; else

-- David Gibson | 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