passt/conf.c, branch 2026_06_11.a9c61ff

conf, util: Disable IPv6 if explicit IPv6 socket probe fails

2026-06-10T14:48:44+00:00

In https://bugs.passt.top/show_bug.cgi?id=188, I originally reported
that if IPv6 is disabled in the kernel (for example via command line
parameter ipv6.disable=1, or disabled in build configuration), and we
attempt to forward any port, we'll exit right away after failing to
set up dual-stack listening sockets.

The original instance of that issue is now fixed for pasta by commit
75dcbc300bf0 ("pasta: Warn, disable matching IP version if not
supported, in local mode") together with the new implementation of
the rule forwarding table, starting from commit b223bec48213 ("fwd,
tcp, udp: Set up listening sockets based on forward table"), because
we first parse forwarding options, then probe for IPv6 support in the
target namespace (and disable IPv6 as a result), and finally bind
sockets once we already know that IPv6 support is disabled.

But we don't do that when invoked as passt, because we have no target
namespace and hence no probing for IPv6 support whatsoever.

Add IPv6 to the socket features we test in sock_probe_features(), and,
if we fail to create an IPv6 socket for whatever reason (which might
include security policies as well), disable IPv6 support altogether,
so that we won't attempt to use dual-stack sockets for port forwarding
either.

Note that the probe comes without any sort of debug message, because
at this point we haven't parsed the configuration yet, and we would
therefore print that regardless of the selected logging level and
other options, including --ipv4-only, which would be rather confusing.
I doubt we'll miss this kind of message though, IPv6 support being
disabled is anyway obvious from the initial configuration dump.

Reported-by: Chi Cuong HA 
Reported-by: Romain Geissler 
Link: https://bugs.passt.top/show_bug.cgi?id=188
Fixes: 4ddd59bc6085 ("conf: Separate local mode for each IP version, don't enable disabled IP version")
Signed-off-by: Stefano Brivio 
Reviewed-by: David Gibson

conf, repair, tap: Document reasons for blocking Unix sockets

2026-05-19T23:23:47+00:00

Most of our operation is asynchronous, based on non-blocking fds handled
in our epoll loop.  However, our several Unix sockets (tap client, repair
helper, control client) are all blocking fds after accept().

That is in fact correct, but for not especially obvious reasons that are
slightly different in each case.  Add explanatory comments to each of them.

Signed-off-by: David Gibson 
[sbrivio: Fixed minor coding style detail in comment in conf_accept()]
Signed-off-by: Stefano Brivio

treewide: Make some additional variables static

2026-05-11T22:04:08+00:00

Mark a number of extra variables local to a single module as static.

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

conf: Fix not-actually-const parameter to conf_runas() and conf_ugid()

2026-05-11T22:03:59+00:00

Commit 4af3d83170fd changed the @opt parameter to conf_runas() to a const
pointer, to remove a cppcheck error.  However, that error was a false
positive.  We *do* modify that parameter via an aliased pointer within it
retreived from strchr().  At least with gcc 16.1.1 that now causes a
"discards const" warning.  Revert that change and instead directly suppress
the cppcheck warning.

Fixes: 4af3d83170fd ("treewide: Fix more pointers which can be const")
Signed-off-by: David Gibson 
Reviewed-by: Laurent Vivier 
Signed-off-by: Stefano Brivio

pesto, conf, fwd_rule: Add options and modes to add, delete, clear rules

2026-05-07T06:06:30+00:00

Instead of just being able to add to the existing tables, implement
an explicit --clear option to replace them, which now becomes the
default behaviour, and implement explicit --add and --delete options
to maintain the table and add or delete specific ports.

The option --clear PIF forces the clearing of a table, instead.

These options can be combined arbitrarily and are handled as
sequential commands, as now described in pesto(1).

If no option is given before forwarding specifiers for a matching
table, the command line is interpreted as a replacement of the
existing rules.

To this end:

- there's no protocol change, as pesto is anyway sending updated
  copies of the table

- the forwarding table functions now include a new fwd_rule_del(),
  which deletes existing rule only if a matching one is found

- a trivial fwd_rule_clear() is factored out from the existing
  conf_handler() implementation, so that it can be directly used
  in pesto

The entry points for parsing of port specifiers now take an additional
'del' parameter which is passed down all the way before reaching the
fwd_rule_add() implementation. If a rule should be deleted, at that
point, fwd_rule_del() is called instead.

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

conf, fwd: Allow switching to new rules received from pesto

2026-05-07T06:06:30+00:00

We can now receive updates to the forwarding rules from the pesto client
and store them in a "pending" copy of the forwarding tables.  Implement
switching to using the new rules.

The logic is in a new fwd_listen_switch().  For now this closes all
listening sockets related to the old tables, swaps the active and pending
tables, then listens based on the new tables.  In future we look to improve
this so that we don't temporarily stop listening on ports that both the
old and new tables specify.

Signed-off-by: David Gibson 
[sbrivio: In fwd_listen_switch(), use the destination size as argument
 to memcpy(), instead of sizeof(tmp), as suggested by Laurent]
Signed-off-by: Stefano Brivio 
Reviewed-by: Laurent Vivier

pesto, conf: Send updated rules from pesto back to passt/pasta

2026-05-07T06:06:30+00:00

Extend pesto to send the updated rule configuration back to passt/pasta.
Extend passt/pasta to read the new configuration and store the new rules in
a "pending" table.   We don't yet attempt to activate them.

Signed-off-by: Stefano Brivio 
[dwg: Based on an early draft from Stefano]
[sbrivio: Add redundant check on interface names being terminated in
 conf_recv_rules(), to make static checkers happy]
[sbrivio: Make conf_recv_rules() return -1 if fwd_rule_read() fails,
 as suggested by Jon Maloy]
[sbrivio: Fix conflicts in Makefile]
Signed-off-by: David Gibson 
Reviewed-by: Laurent Vivier

pesto: Read current ruleset from passt/pasta and optionally display it

2026-05-07T06:06:30+00:00

Implement serialisation of our current forwarding rules in conf.c,
deserialising it to display in the pesto client.  Doing this requires
adding ip.c, inany.c, bitmap.c, lineread.c and fwd_rule.c to the pesto
build.  With previous preparations that now requires only a trivial change
to lineread.c.

Signed-off-by: David Gibson 
Reviewed-by: Laurent Vivier 
[sbrivio: Use ntohs() for rule->to instead of htons() in
 fwd_rule_read(), reported by Jon Maloy]
[sbrivio: Add upper bound check on pc->fwd.count for count of rules
 received by pesto, reported missing by Laurent, plus nits also
 reported by Laurent]
[sbrivio: Fix conflicts in Makefile]
Signed-off-by: Stefano Brivio

pesto: Expose list of pifs to pesto and display them

2026-05-07T06:06:30+00:00

Extend the dynamic update protocol to expose the pif indices and names
from a running passt/pasta to the pesto tool.  pesto records that data
and prints it out.

Signed-off-by: David Gibson 
Reviewed-by: Laurent Vivier 
[sbrivio: In read_pif_conf(), force a redundant termination of the
 interface name, the existing check isn't obvious enough for static
 checkers]
[sbrivio: Drop @resv_ left-over in description of struct
 pesto_pif_info, reported by Jon Maloy]
[sbrivio: Fix minor nits reported by Laurent]
[sbrivio: Initialise struct pesto_pif_info in conf_send_rules() with
 zeroes, otherwise the pif name might be seen as not terminated, and
 we'll expose memory from the back-end]
[sbrivio: Fix conflicts in Makefile]
Signed-off-by: Stefano Brivio

pesto, conf: Have pesto connect to passt and check versions

2026-05-07T06:06:30+00:00

Start implementing pesto in earnest.  Create a control/configuration
socket in passt.  Have pesto connect to it and retrieve a server greeting
Perform some basic version checking.

Signed-off-by: David Gibson 
[sbrivio: Avoid potential recursive calling between conf_accept() and
 conf_close(), reported by clang-tidy]
[sbrivio: In conf(), check we're not exceeding sizeof(c->control_path)
 instead of sizeof(c->socket_path), and, in pesto's main(), print
 argv[optind] instead of argv[1] to indicate an invalid socket path,
 both reported by Jon Maloy]
[sbrivio: In pesto's main(), drop unnecessary newline from error
 message, reported by Laurent]
[sbrivio: Don't use SOCK_NONBLOCK on accept4(), as that only applies
 to the *new* file descriptor, which we don't want -- set O_NONBLOCK
 on the listening file descriptor using fcntl()]
[sbrivio: Switch to protocol version 1, and reflect the true magic
 behind pesto, i.e. basil, into the magic string]
[sbrivio: Fix conflicts in the Makefile caused by the fact that I'm
 not merging a previous series reworking it]
Signed-off-by: Stefano Brivio 
Reviewed-by: Laurent Vivier