From: Pascal Mazon <pascal.mazon@6wind.com>
To: Ophir Munk <ophirmu@mellanox.com>, dev@dpdk.org
Cc: Thomas Monjalon <thomas@monjalon.net>, Olga Shern <olgas@mellanox.com>
Subject: Re: [dpdk-dev] [PATCH v2] net/tap: fix eBPF handling of non-RSS flows
Date: Mon, 5 Feb 2018 15:51:09 +0100 [thread overview]
Message-ID: <82465840-531b-8ce5-eb0d-a9fe4c962542@6wind.com> (raw)
In-Reply-To: <1517841642-10429-2-git-send-email-ophirmu@mellanox.com>
The mitigation is good enough, random packets are more likely to have
cb[1] == 0 than something above 7cafe800.
Acked-by: Pascal Mazon <pascal.mazon@6wind.com>
On 05/02/2018 15:40, Ophir Munk wrote:
> The eBPF classifier (section "cls_q" in tap_bpf_program.c) is tracing
> marked packets in which skb->cb[1] contains an RSS queue number, and
> redirects those packets to the matched queue.
> It is expected that skb->cb[1] has been previously set with a valid RSS
> queue number during an eBPF action (section "l3_l4" in tap_bpf_program.c).
> However, for non-RSS flows, skb->cb[1] may contain a random unset value,
> which could falsely be interpreted as a valid RSS queue.
> To avoid this potential error, tap_bpf_program.c has been updated as
> follows:
> 1. After calculating the RSS queue number, it is added a unique offset in
> order to uniquely identify it as a valid RSS queue number.
> 2. After matching an RSS queue to a packet, skb->cb[1] is set to 0.
>
> Fixes: cdc07e83bb24 ("net/tap: add eBPF program file")
> Fixes: aabe70df73a3 ("net/tap: add eBPF bytes code")
>
> Signed-off-by: Ophir Munk <ophirmu@mellanox.com>
> ---
> drivers/net/tap/tap_bpf_insns.h | 23 +++++++++++++----------
> drivers/net/tap/tap_bpf_program.c | 9 ++++++---
> 2 files changed, 19 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/net/tap/tap_bpf_insns.h b/drivers/net/tap/tap_bpf_insns.h
> index c406f78..89873b6 100644
> --- a/drivers/net/tap/tap_bpf_insns.h
> +++ b/drivers/net/tap/tap_bpf_insns.h
> @@ -6,17 +6,20 @@
>
> /* bpf_insn array matching cls_q section. See tap_bpf_program.c file */
> struct bpf_insn cls_q_insns[] = {
> - {0x61, 1, 1, 52, 0x00000000},
> - {0x18, 2, 0, 0, 0xdeadbeef},
> + {0x61, 2, 1, 52, 0x00000000},
> + {0x18, 3, 0, 0, 0xdeadbeef},
> {0x00, 0, 0, 0, 0x00000000},
> - {0x63, 10, 2, -4, 0x00000000},
> - {0x61, 2, 10, -4, 0x00000000},
> - {0x07, 2, 0, 0, 0x00000001},
> - {0x67, 2, 0, 0, 0x00000020},
> - {0x77, 2, 0, 0, 0x00000020},
> - {0xb7, 0, 0, 0, 0xffffffff},
> - {0x1d, 1, 2, 1, 0x00000000},
> + {0x63, 10, 3, -4, 0x00000000},
> {0xb7, 0, 0, 0, 0x00000000},
> + {0x61, 3, 10, -4, 0x00000000},
> + {0x07, 3, 0, 0, 0x7cafe800},
> + {0x67, 3, 0, 0, 0x00000020},
> + {0x77, 3, 0, 0, 0x00000020},
> + {0x5d, 2, 3, 4, 0x00000000},
> + {0xb7, 2, 0, 0, 0x00000000},
> + {0x63, 1, 2, 52, 0x00000000},
> + {0x18, 0, 0, 0, 0xffffffff},
> + {0x00, 0, 0, 0, 0x00000000},
> {0x95, 0, 0, 0, 0x00000000},
> };
>
> @@ -1685,7 +1688,7 @@ struct bpf_insn l3_l4_hash_insns[] = {
> {0x4f, 3, 2, 0, 0x00000000},
> {0x67, 3, 0, 0, 0x00000010},
> {0x4f, 3, 1, 0, 0x00000000},
> - {0x07, 3, 0, 0, 0x00000001},
> + {0x07, 3, 0, 0, 0x7cafe800},
> {0x63, 5, 3, 52, 0x00000000},
> {0xb7, 7, 0, 0, 0x00000001},
> {0xbf, 0, 7, 0, 0x00000000},
> diff --git a/drivers/net/tap/tap_bpf_program.c b/drivers/net/tap/tap_bpf_program.c
> index 848c50b..8abb3b7 100644
> --- a/drivers/net/tap/tap_bpf_program.c
> +++ b/drivers/net/tap/tap_bpf_program.c
> @@ -28,10 +28,10 @@
> ((b) & 0xff))
>
> /*
> - * The queue number is offset by 1, to distinguish packets that have
> - * gone through this rule (skb->cb[1] != 0) from others.
> + * The queue number is offset by a unique QUEUE_OFFSET, to distinguish
> + * packets that have gone through this rule (skb->cb[1] != 0) from others.
> */
> -#define QUEUE_OFFSET 1
> +#define QUEUE_OFFSET 0x7cafe800
> #define PIN_GLOBAL_NS 2
>
> #define KEY_IDX 0
> @@ -63,6 +63,9 @@ match_q(struct __sk_buff *skb)
>
> if (queue != match_queue)
> return TC_ACT_OK;
> +
> + /* queue match */
> + skb->cb[1] = 0;
> return TC_ACT_UNSPEC;
> }
>
next prev parent reply other threads:[~2018-02-05 14:51 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-03 23:34 [dpdk-dev] [PATCH v1] " Ophir Munk
2018-02-05 14:40 ` [dpdk-dev] [PATCH v2] fix eBPF handling for non-RSS rules Ophir Munk
2018-02-05 14:40 ` [dpdk-dev] [PATCH v2] net/tap: fix eBPF handling of non-RSS flows Ophir Munk
2018-02-05 14:51 ` Pascal Mazon [this message]
2018-02-05 18:10 ` Ferruh Yigit
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=82465840-531b-8ce5-eb0d-a9fe4c962542@6wind.com \
--to=pascal.mazon@6wind.com \
--cc=dev@dpdk.org \
--cc=olgas@mellanox.com \
--cc=ophirmu@mellanox.com \
--cc=thomas@monjalon.net \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).