passt/packet.c, 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: 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

ip: Use iov_tail in ipv6_l4hdr()

2025-09-03T18:43:31+00:00

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

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

arp: Convert to iov_tail

2025-09-03T18:42:26+00:00

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

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: Upgrade severity of most packet errors

2025-03-20T19:33:30+00:00

All errors from packet_range_check(), packet_add() and packet_get() are
trace level.  However, these are for the most part actual error conditions.
They're states that should not happen, in many cases indicating a bug
in the caller or elswhere.

We don't promote these to err() or ASSERT() level, for fear of a localised
bug on very specific input crashing the entire program, or flooding the
logs, but we can at least upgrade them to debug level.

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

packet: ASSERT on signs of pool corruption

2025-03-20T19:33:27+00:00

If packet_check_range() fails in packet_get_try_do() we just return NULL.
But this check only takes places after we've already validated the given
range against the packet it's in.  That means that if packet_check_range()
fails, the packet pool is already in a corrupted state (we should have
made strictly stronger checks when the packet was added).  Simply returning
NULL and logging a trace() level message isn't really adequate for that
situation; ASSERT instead.

Similarly we check the given idx against both p->count and p->size.  The
latter should be redundant, because count should always be <= size.  If
that's not the case then, again, the pool is already in a corrupted state
and we may have overwritten unknown memory.  Assert for this case too.

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