As we support UDP forwarding for packets that are sent to local
ports, we actually need some kind of connection tracking for UDP.
While at it, this commit introduces a number of vaguely related fixes
for issues observed while trying this out. In detail:
- implement an explicit, albeit minimalistic, connection tracking
for UDP, to allow usage of ephemeral ports by the guest and by
the host at the same time, by binding them dynamically as needed,
and to allow mapping address changes for packets with a loopback
address as destination
- set the guest MAC address whenever we receive a packet from tap
instead of waiting for an ARP request, and set it to broadcast on
start, otherwise DHCPv6 might not work if all DHCPv6 requests time
out before the guest starts talking IPv4
- split context IPv6 address into address we assign, global or site
address seen on tap, and link-local address seen on tap, and make
sure we use the addresses we've seen as destination (link-local
choice depends on source address). Similarly, for IPv4, split into
address we assign and address we observe, and use the address we
observe as destination
- introduce a clock_gettime() syscall right after epoll_wait() wakes
up, so that we can remove all the other ones and pass the current
timestamp to tap and socket handlers -- this is additionally needed
by UDP to time out bindings to ephemeral ports and mappings between
loopback address and a local address
- rename sock_l4_add() to sock_l4(), no semantic changes intended
- include <arpa/inet.h> in passt.c before kernel headers so that we
can use <netinet/in.h> macros to check IPv6 address types, and
remove a duplicate <linux/ip.h> inclusion
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
It looks like some versions of ISC's IPv6 dhclient not only discard
the DNS Recursive Name Server option if other options (Domain Search
List? FQDN?) are absent, but they also drop existing entries
configured via SLAAC from /etc/resolv.conf.
Don't pass option 23 until I figure this out, it's anyway redundant
as we pass DNS information via SLAAC (RFC 8106).
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
dhcpv6_opt() needs to subtract option length _before_ returning,
so that callers can conveniently pass the remaining length on
subsequent calls.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
The NotOnLink status code needs to be appended to the existing IA
content, because if we omit the requested addresses in the reply,
ISC's dhclient handles it as a NoAddrsAvail response.
Also fix length accounting (we would send a bunch of zeroes after
the IA otherwise), and print an informational message with the
requested address, if it's not appropriate for the link.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This implementation, similarly to the IPv4 DHCP one, hands out a
single address, which is the same as the upstream address for the
host.
This avoids the need for address translation as long as the client
runs a DHCPv6 client. The NDP "Managed" flag is now set in Router
Advertisements.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
