passt/iov.c, branch 2026_05_07.1afd4ed

treewide: Spell ASSERT() as assert()

2026-03-20T20:05:29+00:00

The standard library assert(3), at least with glibc, hits our seccomp
filter and dies with SIGSYS before it's able to print a message, making it
near useless.  Therefore, since 7a8ed9459dfe ("Make assertions actually
useful") we've instead used our own implementation, named ASSERT().

This makes our code look slightly odd though - ASSERT() has the same
overall effect as assert(), it's just a different implementation.  More
importantly this makes it awkward to share code between passt/pasta proper
and things that compile in a more typical environment.  We're going to want
that for our upcoming dynamic configuration tool.

Address this by overriding the standard library's assert() implementation
with our own, instead of giving ours its own name.

The standard assert() is supposed to be omitted if NDEBUG is defined,
which ours doesn't do.  Implement that as well, so ours doesn't
unexpectedly differ.  For the -DNDEBUG case we do this by *not* overriding
assert(), since it will be a no-op anyway.  This requires a few places to
add a #include  to let us compile (albeit with warnings) when
-DNDEBUG.

Signed-off-by: David Gibson 
[sbrivio: Fix some conflicts and missing conversions as a result of
 applying "vu_common: Move iovec management into vu_collect()" first]
Signed-off-by: Stefano Brivio

iov: Add iov_truncate() helper and use it in vu handlers

2026-03-10T14:26:43+00:00

Add a generic iov_truncate() function that truncates an IO vector to a
given number of bytes, returning the number of iov entries that contain
data after truncation.

Use it in udp_vu_sock_recv() and tcp_vu_sock_recv() to replace the
open-coded truncation logic that adjusted iov entries after recvmsg().
Also convert the direct iov_len assignment in tcp_vu_send_flag() to use
iov_truncate() for consistency.

Add an ASSERT() in tcp_vu_data_from_sock() to quiet the Coverity error:

passt/tcp_vu.c:457:3:
  19. overflow_const: Expression "dlen + hdrlen", where "dlen" is known to
      be equal to -86,  and "hdrlen" is known to be equal to 86, underflows
      the type of "dlen + hdrlen", which is type "unsigned long".

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

iov: Fix coding style of basic (non-IOV_TAIL) parts

2025-12-08T03:47:57+00:00

I happened to touch these functions for a change that turned out to be
unnecessary, but coding style and documentation could still benefit
from some rephrasing and fixes.

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

dhcpv6: Use iov_tail in dhcpv6_opt()

2025-09-03T18:43:27+00:00

dhcpv6_opt() and its callers are refactored for iov_tail option parsing,
replacing direct offset management for improved robustness.

Its signature is now `bool dhcpv6_opt(iov_tail *data, type)`. `*data` (in/out)
points to a found option on `true` return or is restored on `false`.
The main dhcpv6() function uses IOV_REMOVE_HEADER for the msg_hdr, then
passes the iov_tail (now at options start) to the new dhcpv6_opt().

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

icmp: Convert to iov_tail

2025-09-03T18:42:30+00:00

Use packet_data() and extract headers using IOV_PEEK_HEADER()
rather than packet_get().

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

tap: Use iov_tail with tap_add_packet()

2025-09-03T18:42:20+00:00

Use IOV_PEEK_HEADER() to get the ethernet header from the iovec.

Move the workaround about multiple iovec array from vu_handle_tx() to
tap_add_packet(). Removing the offset out of the iovec array should
reduce the iovec count to 1.

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

iov: Update IOV_REMOVE_HEADER() and IOV_PEEK_HEADER()

2025-09-03T18:42:17+00:00

Provide a temporary variable of the wanted type to store
the header if the memory in the iovec array is not contiguous.

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

iov: Introduce iov_tail_clone() and iov_drop_header().

2025-09-03T18:42:15+00:00

These utilities enhance iov_tail manipulation, useful for
efficient packet processing by enabling iovec array cloning and
header stripping without data copies.

- iov_drop_header(): Discards a specified number of bytes from the
  beginning of an iov_tail by advancing its internal offset and pruning
  consumed elements.

- iov_tail_clone(): Clone an iov_tail into an iovec array, adjusting the
first iovec entry to remove the iov_tail offset.

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

style: Add parentheses to function names in comments

2025-07-18T17:19:37+00:00

The commit updates the style of function comments by adding parentheses
to function names in the descriptions where they are missing.

Done with:

---------8<------ fix_function_name.awk ---------8<------
/^\/\*\*/ {
    check_next = 1;
    print $0
    next
}
check_next == 1 && / \* struct/ {
    check_next = 0
    print $0
    next
}
check_next == 1 && / \* enum/ {
    check_next = 0
    print $0
    next
}
check_next == 1 && /^ \* [^ (]* -/ {
   modified_line = gensub(/^ \* ([^ ]*) -(.*)$/, " * \\1() -\\2", "g", $0)
   print modified_line
   check_next = 0;
   next
}
{
    print $0
    check_next = 0
}
---------8<------ fix_function_name.awk ---------8<------

Then

for file in *.[ch]; do
    cp ${file} ${file}.tmp && \
    awk -f fix_function_name.awk ${file}.tmp > ${file}
done

Signed-off-by: Laurent Vivier 
Signed-off-by: Stefano Brivio

style: Fix 'Return' comment style

2025-07-18T17:19:24+00:00

We always use imperative (no 'Returns:'), no tab after the ':' and
only one space, the first character is always lowercase.

This is fixed with:

 sed -i "s/Returns:/Return:/;s/Return:    /Return: /;s/Return:  */Return: /;s/Return: \([A-Z]\)/Return: \L\1/" *.[ch]

And manually updated to fix alignment of multiline comment and words
that must keep uppercase (like IPv4, TCP, UDP, Layer-4).

Signed-off-by: Laurent Vivier 
Signed-off-by: Stefano Brivio