Re: [PATCH 1/7] tap: Move the tap_hdr file to a separate file

[Laurent Vivier <lvivier@redhat.com>]

On 9/9/26 11:10, David Gibson wrote:
> On Wed, Sep 09, 2026 at 10:47:25AM +0200, Laurent Vivier wrote:
>> Subject: s/tap_hdr file/tap_hdr structure/
>>
>>
>> On 9/4/26 23:28, aerosouund wrote:
>>> From: Ammar Yasser <aerosound161@gmail.com>
>>>
>>> It was defined in tap.h, put it on its own so that future callers won't
>>> need to depend on all definitions in tap.h.
>>> Also turn it into a union of a vnet_len and virtio_net_mrg_rxbuf
>>> because for vhost acceleration the frames will have this virtio net
>>> header prepended to them.
>>>
>>> Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
>>
>> If Eugenio is the author, you should set it as the author, otherwise you
>> should remove his Signed-off-by
> 
> I don't think that's necessarily correct.  If the patch has been
> changed substantially enough from the original, it makes sense to
> change the author.  However, the S-o-b should remain if some fragments
> of the original remain, so as to still record the chain of hands
> through which it has passed for the DCO.

I understand and I agree with that but after checking I don't see these changes in 
Eugenio's series.

Laurent>
>>
>>> Signed-off-by: Ammar Yasser <aerosound161@gmail.com>
>>> ---
>>>    tap.h     |  9 +--------
>>>    tap_hdr.h | 23 +++++++++++++++++++++++
>>>    2 files changed, 24 insertions(+), 8 deletions(-)
>>>    create mode 100644 tap_hdr.h
>>>
>>> diff --git a/tap.h b/tap.h
>>> index b335933..1625975 100644
>>> --- a/tap.h
>>> +++ b/tap.h
>>> @@ -10,6 +10,7 @@
>>>    #include <stdint.h>
>>>    #include "passt.h"
>>> +#include "tap_hdr.h"
>>>    /** L2_MAX_LEN_PASTA - Maximum frame length for pasta mode (with L2 header)
>>>     *
>>> @@ -38,14 +39,6 @@
>>>    struct udphdr;
>>> -/**
>>> - * struct tap_hdr - tap backend specific headers
>>> - * @vnet_len:	Frame length (for qemu socket transport)
>>> - */
>>> -struct tap_hdr {
>>> -	uint32_t vnet_len;
>>> -} __attribute__((packed));
>>> -
>>>    /**
>>>     * tap_hdr_iov() - struct iovec for a tap header
>>>     * @c:		Execution context
>>> diff --git a/tap_hdr.h b/tap_hdr.h
>>> new file mode 100644
>>> index 0000000..aa270b7
>>> --- /dev/null
>>> +++ b/tap_hdr.h
>>> @@ -0,0 +1,23 @@
>>> +/* SPDX-License-Identifier: GPL-2.0-or-later
>>> + * Copyright (c) 2021 Red Hat GmbH
>>> + * Author: Stefano Brivio <sbrivio@redhat.com>
>>> + */
>>> +
>>> +#ifndef TAP_HDR_H
>>> +#define TAP_HDR_H
>>> +
>>> +#include <stdint.h>
>>> +#include <linux/virtio_net.h>
>>> +
>>> +/**
>>> + * struct tap_hdr - tap backend specific headers
>>> + * @vnet_len:	Frame length (for qemu socket transport)
>>
>> missing @hdr description
>>
>>> + */
>>> +struct tap_hdr {
>>> +	union {
>>> +		uint32_t vnet_len;
>>> +		struct virtio_net_hdr_mrg_rxbuf hdr;
>>> +	};
>>> +};
>>
>> This will break passt.
>>
>> In tap.h, we have:
>> static inline struct iovec tap_hdr_iov(const struct ctx *c,
>>                                         struct tap_hdr *thdr)
>> {
>>          return (struct iovec){
>>                  .iov_base = thdr,
>>                  .iov_len = c->mode == MODE_PASST ? sizeof(*thdr) : 0,
>>          };
>> }
>>
>> before this patch sizeof(*thdr) is 4, now it's 12.
>>
>>> +
>>> +#endif /* TAP_HDR_H */
>>
>