passt/dhcpv6.h, branch 2026_07_16.090d739

dhcpv6: Fix reply destination to match client's source address

2026-07-14T23:21:20+00:00

tap_ip6_daddr() selects the reply destination based on our source
address type (link-local), so it always returns addr_ll_seen. But if
the client sent from a global address, we would reply to an address
different from what the client is expecting. Since RFC 9915 (section
18.3.10) allows clients to use global addresses for DHCPv6, we now
correct this, and always respond to the address the client was using.

We also remove a redundant addr_ll_seen assignment, since this is
already done by tap.c when processing IPv6 packets.

Note: if the client uses a global source address, our reply will
still have a link-local source, creating a scope mismatch. Fixing
this properly would require a mechanism to allocate a global address
for the DHCPv6 server, which we currently don't have. Responding to
the client's actual source address is still a net improvement over the
previous behavior of replying to an unrelated cached address.

Note 2: This commit isn't actually a fix to an observed problem, but
rather an answer to a theoretical issue, adding completeness to the
mechanism and simplifying subsequent changes in this series.

Signed-off-by: Jon Maloy 
Reviewed-by: David Gibson 
Signed-off-by: Stefano Brivio

dhcpv6: use iov_tail rather than pool

2025-09-03T18:43:41+00:00

This patch refactors the dhcpv6() function to accept `struct iov_tail *data`
directly as its packet input, replacing the `const struct pool *p` parameter.
Consequently, dhcpv6() no longer fetches packet data internally using
packet_data().

This change simplifies callers, such as tap6_handler(), which now pass
the iov_tail representing the L4 UDP segment (DHCPv6 message) directly.
This removes the need for intermediate packet pool handling.

Signed-off-by: Laurent Vivier 
Reviewed-by: David Gibson 
Signed-off-by: Stefano Brivio

passt: Relicense to GPL 2.0, or any later version

2023-04-06T16:00:33+00:00

In practical terms, passt doesn't benefit from the additional
protection offered by the AGPL over the GPL, because it's not
suitable to be executed over a computer network.

Further, restricting the distribution under the version 3 of the GPL
wouldn't provide any practical advantage either, as long as the passt
codebase is concerned, and might cause unnecessary compatibility
dilemmas.

Change licensing terms to the GNU General Public License Version 2,
or any later version, with written permission from all current and
past contributors, namely: myself, David Gibson, Laine Stump, Andrea
Bolognani, Paul Holzinger, Richard W.M. Jones, Chris Kuhn, Florian
Weimer, Giuseppe Scrivano, Stefan Hajnoczi, and Vasiliy Ulyanov.

Signed-off-by: Stefano Brivio

treewide: Mark constant references as const

2022-03-29T13:35:38+00:00

Signed-off-by: Stefano Brivio

treewide: Add include guards

2022-03-29T13:35:38+00:00

...at the moment, just for consistency with packet.h, icmp.h,
tcp.h and udp.h.

Signed-off-by: Stefano Brivio

treewide: Packet abstraction with mandatory boundary checks

2022-03-29T13:35:38+00:00

Implement a packet abstraction providing boundary and size checks
based on packet descriptors: packets stored in a buffer can be queued
into a pool (without storage of its own), and data can be retrieved
referring to an index in the pool, specifying offset and length.

Checks ensure data is not read outside the boundaries of buffer and
descriptors, and that packets added to a pool are within the buffer
range with valid offset and indices.

This implies a wider rework: usage of the "queueing" part of the
abstraction mostly affects tap_handler_{passt,pasta}() functions and
their callees, while the "fetching" part affects all the guest or tap
facing implementations: TCP, UDP, ICMP, ARP, NDP, DHCP and DHCPv6
handlers.

Suggested-by: Stefan Hajnoczi 
Signed-off-by: Stefano Brivio

LICENSES: Add license text files, add missing notices, fix SPDX tags

2021-10-20T06:29:30+00:00

SPDX tags don't replace license files. Some notices were missing and
some tags were not according to the SPDX specification, too.

Now reuse --lint from the REUSE tool (https://reuse.software/) passes.

Reported-by: Martin Hauke 
Signed-off-by: Stefano Brivio

passt: Introduce a DHCPv6 server

2021-04-13T20:37:40+00:00

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