passt/packet.h, branch bug165c

packet: Add support for multi-vector packets

2025-09-03T18:43:51+00:00

The packet pool was previously limited to handling packets contained
within a single buffer.

This patch extends the packet pool to support iovec array,
allowing a single logical packet to be composed of multiple iovec.

To accommodate this, the storage format within the pool is modified.
For a multi-vector packet, a header entry is now stored first with
iov_base = NULL and iov_len holding the number of subsequent
vectors. The actual data vectors are then stored in the following
pool slots.

The packet_add_do() and packet_get_do() functions are updated to
manage this new format for storing and retrieving packets. The
pool_full() check is also adjusted to ensure there is enough
space for all vectors of a new packet before adding it.

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

packet: Refactor vhost-user memory region handling

2025-09-03T18:43:48+00:00

This patch refactors the handling of vhost-user memory regions by
introducing a new `struct vdev_memory` to encapsulate the regions
array and their count (`nregions`) within the main `vu_dev` structure.

This new `vdev_memory` structure is then passed to the packet pool by
re-using the existing `p->buf` field. A `p->buf_size` of 0 indicates
that `p->buf` holds a pointer to `struct vdev_memory` instead of a
regular packet buffer. A new helper, `get_vdev_memory()`, is added to
abstract this access pattern.

Previous implementation was using a marker at the end of the memory
regions array. We can now uses all the slots.

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

packet: remove unused parameter from PACKET_POOL_DECL()

2025-09-03T18:43:47+00:00

_buf is not used in the macro. Remove it.
Remove it also from PACKET_POOL_NOINIT() as it was needed
for PACKET_POOL_DECL().

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

packet: remove PACKET_POOL() and PACKET_POOL_P()

2025-09-03T18:43:45+00:00

These macros are no longer used following the refactoring of packet
handlers to directly use iov_tail. Callers no longer require PACKET_POOL_P
for temporary pools, and PACKET_POOL can be replaced by PACKET_POOL_DECL
and separate initialization if needed.

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

packet: rename packet_data() to packet_get()

2025-09-03T18:43:35+00:00

As we have removed packet_get(), we can rename packet_data() to packet_get()
as the name is clearer.

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

tap: Convert tap6_handler() to iov_tail

2025-09-03T18:43:34+00:00

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

Remove packet_get() as it is not used anymore.

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

packet: Add packet_data()

2025-09-03T18:42:23+00:00

packet_data() gets the data range from a packet descriptor from a
given pool.

It uses iov_tail to return the packet memory.

packet_data() will be renamed to replace packet_get() later.

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

packet: Use iov_tail with packet_add()

2025-09-03T18:42:21+00:00

Modify the interface of packet_add_do() to take an iov_tail
rather than a memory pointer and length.

Internally it only supports iovec array with only one entry,
after being pruned. We can accept iovec array with several
entries if the offset allows the function to reduce the number
of entries to 1.

tap4_handler() is updated to create an iov_tail value using
IOV_TAIL_FROM_BUF() from the buffer and the length.

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

packet: Rework packet_get() versus packet_get_try()

2025-03-20T19:33:22+00:00

Most failures of packet_get() indicate a serious problem, and log messages
accordingly.  However, a few callers expect failures here, because they're
probing for a certain range which might or might not be in a packet.  They
use packet_get_try() which passes a NULL func to packet_get_do() to
suppress the logging which is unwanted in this case.

However, this doesn't just suppress the log when packet_get_do() finds the
requested region isn't in the packet.  It suppresses logging for all other
errors too, which do indicate serious problems, even for the callers of
packet_get_try().  Worse it will pass the NULL func on to
packet_check_range() which doesn't expect it, meaning we'll get unhelpful
messages from there if there is a failure.

Fix this by making packet_get_try_do() the primary function which doesn't
log for the case of a range outside the packet.  packet_get_do() becomes a
trivial wrapper around that which logs a message if packet_get_try_do()
returns NULL.

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

packet: Correct type of PACKET_MAX_LEN

2025-03-20T19:33:15+00:00

PACKET_MAX_LEN is usually involved in calculations on size_t values - the
type of the iov_len field in struct iovec.  However, being defined bare as
UINT16_MAX, the compiled is likely to assign it a shorter type.  This can
lead to unexpected promotions (or lack thereof).  Add a cast to force the
type to be what we expect.

Fixes: c43972ad6 ("packet: Give explicit name to maximum packet size")
Signed-off-by: David Gibson 
Signed-off-by: Stefano Brivio