From: Laurent Vivier <lvivier@redhat.com>
To: David Gibson <david@gibson.dropbear.id.au>
Cc: passt-dev@passt.top
Subject: Re: [PATCH v5 1/8] tcp: extract buffer management from tcp_send_flag()
Date: Tue, 11 Jun 2024 13:42:20 +0200 [thread overview]
Message-ID: <ab664cdb-bb99-48ae-95c9-d0b7ceed4ba1@redhat.com> (raw)
In-Reply-To: <ZmfhRPSjwquWEPa_@zatzit>
On 11/06/2024 07:31, David Gibson wrote:
> On Wed, Jun 05, 2024 at 05:21:22PM +0200, Laurent Vivier wrote:
>> This commit isolates the internal data structure management used for storing
>> data (e.g., tcp4_l2_flags_iov[], tcp6_l2_flags_iov[], tcp4_flags_ip[],
>> tcp4_flags[], ...) from the tcp_send_flag() function. The extracted
>> functionality is relocated to a new function named tcp_fill_flag_header().
>>
>> tcp_fill_flag_header() is now a generic function that accepts parameters such
>> as struct tcphdr and a data pointer. tcp_send_flag() utilizes this parameter to
>> pass memory pointers from tcp4_l2_flags_iov[] and tcp6_l2_flags_iov[].
>>
>> This separation sets the stage for utilizing tcp_fill_flag_header() to
>> set the memory provided by the guest via vhost-user in future developments.
>
> Thanks for the commit message, it makes this much clearer.
>
> I have a number of comments below, but they're basically all cosmetic.
>
>> Signed-off-by: Laurent Vivier <lvivier@redhat.com>
>> ---
>> tcp.c | 63 ++++++++++++++++++++++++++++++++++++-----------------------
>> 1 file changed, 39 insertions(+), 24 deletions(-)
>>
>> diff --git a/tcp.c b/tcp.c
>> index 06acb41e4d90..68d4afa05a36 100644
>> --- a/tcp.c
>> +++ b/tcp.c
>> @@ -1549,24 +1549,25 @@ static void tcp_update_seqack_from_tap(const struct ctx *c,
>> }
>>
>> /**
>> - * tcp_send_flag() - Send segment with flags to tap (no payload)
>> + * tcp_fill_flag_header() - Prepare header for flags-only segment (no payload)
>
> I don't love the name tcp_fill_flag_header(), although it's not
> terrible. Maybe tcp_prepare_flags() would be better?
>
>> * @c: Execution context
>> * @conn: Connection pointer
>> * @flags: TCP flags: if not set, send segment only if ACK is due
>> + * @th: TCP header to update
>> + * @data: buffer to store TCP option
>> + * @optlen: size of the TCP option buffer
>
> Worth noting this is an output parameter here...
>
>> *
>> - * Return: negative error code on connection reset, 0 otherwise
>> + * Return: < 0 error code on connection reset,
>> + * 0 if there is no flag to send
>> + * 1 otherwise
>
> .. or, since optlen will always be positive on success cases, you
> could just return it.
>
We cannot return optlen here as optlen can be 0 (it is not zero only with SYN), and 0
means no flags to send. We can have flags to send with optlen equal to 0.
Thanks,
Laurent
next prev parent reply other threads:[~2024-06-11 11:42 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-06-05 15:21 [PATCH v5 0/8] Add vhost-user support to passt (part 2) Laurent Vivier
2024-06-05 15:21 ` [PATCH v5 1/8] tcp: extract buffer management from tcp_send_flag() Laurent Vivier
2024-06-11 5:31 ` David Gibson
2024-06-11 11:42 ` Laurent Vivier [this message]
2024-06-12 6:31 ` David Gibson
2024-06-11 22:09 ` Stefano Brivio
2024-06-12 6:32 ` David Gibson
2024-06-05 15:21 ` [PATCH v5 2/8] tcp: move buffers management functions to their own file Laurent Vivier
2024-06-11 22:09 ` Stefano Brivio
2024-06-12 6:14 ` David Gibson
2024-06-12 12:03 ` Stefano Brivio
2024-06-05 15:21 ` [PATCH v5 3/8] tap: refactor packets handling functions Laurent Vivier
2024-06-11 22:09 ` Stefano Brivio
2024-06-12 6:18 ` David Gibson
2024-06-12 6:34 ` Stefano Brivio
2024-06-12 6:37 ` David Gibson
2024-06-12 6:21 ` David Gibson
2024-06-05 15:21 ` [PATCH v5 4/8] udp: refactor UDP header update functions Laurent Vivier
2024-06-11 22:10 ` Stefano Brivio
2024-06-12 6:27 ` David Gibson
2024-06-05 15:21 ` [PATCH v5 5/8] udp: rename udp_sock_handler() to udp_buf_sock_handler() Laurent Vivier
2024-06-12 6:28 ` David Gibson
2024-06-05 15:21 ` [PATCH v5 6/8] vhost-user: compare mode MODE_PASTA and not MODE_PASST Laurent Vivier
2024-06-11 22:10 ` Stefano Brivio
2024-06-05 15:21 ` [PATCH v5 7/8] iov: remove iov_copy() Laurent Vivier
2024-06-05 15:21 ` [PATCH v5 8/8] tap: use in->buf_size rather than sizeof(pkt_buf) Laurent Vivier
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