From: Stephen Hemminger <stephen@networkplumber.org>
To: "Mário Kuka" <kuka@cesnet.cz>
Cc: Reshma Pattan <reshma.pattan@intel.com>,
Ray Kinsella <mdr@ashroe.eu>,
dev@dpdk.org
Subject: Re: [PATCH] pcapng: fix write more packets than IOV_MAX limit
Date: Mon, 25 Jul 2022 08:57:44 -0700 [thread overview]
Message-ID: <20220725085744.6724e7c3@hermes.local> (raw)
In-Reply-To: <20220725152811.409447-1-kuka@cesnet.cz>
On Mon, 25 Jul 2022 17:28:11 +0200
Mário Kuka <kuka@cesnet.cz> wrote:
> The rte_pcapng_write_packets() function fails when we try to write more
> packets than the IOV_MAX limit. The error is caused by the writev()
> system call, which is limited by the IOV_MAX limit. The iovcnt argument
> is valid if it is greater than 0 and less than or equal to IOV_MAX as
> defined in <limits.h>.
>
> To avoid this problem, we can split the iovec buffer into smaller
> chunks with a maximum size of IOV_MAX and write them sequentially by
> calling the writev() repeatedly.
That risks writing partial packets.
Better to move the break down inside the logic of rte_pcapng_write_packets()
and at the same time, remove the VLA of iov[iovcnt]
>
> Fixes: 8d23ce8f5ee9 ("pcapng: add new library for writing pcapng files")
> Cc: stephen@networkplumber.org
>
> Signed-off-by: Mário Kuka <kuka@cesnet.cz>
What is the burst size here?
IOV_MAX is 1024, and typical max mbuf per packet would be 5
that means as is the code works for up to 204 burst size.
Sure you can use DPDK in odd ways with small mbuf sizes and huge
burst sizes, but this needs to only in some slow path.
next prev parent reply other threads:[~2022-07-25 15:57 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-25 15:28 Mário Kuka
2022-07-25 15:57 ` Stephen Hemminger [this message]
2022-07-25 16:10 ` Stephen Hemminger
2022-07-29 7:18 ` [PATCH v2 0/2] pcapng: fix some issues with writing packets Mário Kuka
2022-07-29 7:18 ` [PATCH v2 1/2] pcapng: fix write more packets than IOV_MAX limit Mário Kuka
2022-07-29 7:18 ` [PATCH v2 2/2] pcapng: check if writev() returns a partial write Mário Kuka
2022-07-29 16:00 ` Stephen Hemminger
2022-07-29 17:08 ` Mário Kuka
2022-07-29 18:14 ` Stephen Hemminger
2022-08-01 8:42 ` Mário Kuka
2022-07-29 15:58 ` [PATCH v2 0/2] pcapng: fix some issues with writing packets Stephen Hemminger
2022-07-29 17:33 ` Mário Kuka
2022-08-01 8:40 ` [PATCH v3] pcapng: fix write more packets than IOV_MAX limit Mário Kuka
2022-08-01 15:33 ` Stephen Hemminger
2022-10-10 0:40 ` Thomas Monjalon
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