From: "Krzysztof Hałasa" <khalasa@piap.pl>
To: Xie He <xie.he.0141@gmail.com>
Cc: Jakub Kicinski <kuba@kernel.org>,
Krzysztof Halasa <khc@pm.waw.pl>,
"David S. Miller" <davem@davemloft.net>,
Linux Kernel Network Developers <netdev@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Martin Schiller <ms@dev.tdt.de>,
Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Subject: Re: [PATCH net v2] drivers/net/wan/hdlc_fr: Add needed_headroom for PVC devices
Date: Mon, 14 Sep 2020 07:26:12 +0200 [thread overview]
Message-ID: <m3v9ghgc97.fsf@t19.piap.pl> (raw)
In-Reply-To: <CAJht_EN+=WTuduvm43_Lq=XWL78AcF5q6Zoyg8S5fao_udL=+Q@mail.gmail.com> (Xie He's message of "Fri, 4 Sep 2020 18:28:38 -0700")
Xie He <xie.he.0141@gmail.com> writes:
> The HDLC device is not actually prepending any header when it is used
> with this driver. When the PVC device has prepended its header and
> handed over the skb to the HDLC device, the HDLC device just hands it
> over to the hardware driver for transmission without prepending any
> header.
That's correct. IIRC:
- Cisco and PPP modes add 4 bytes
- Frame Relay adds 4 (specific protocols - mostly IPv4) or 10 (general
case) bytes. There is that pvcX->hdlcX transition which adds nothing
(the header is already in place when the packet leaves pvcX device).
- Raw mode adds nothing (IPv4 only, though it could be modified for
both IPv4/v6 easily)
- Ethernet (hdlc_raw_eth.c) adds normal Ethernet header.
(I had been "unplugged" for some time).
--
Krzysztof Halasa
Sieć Badawcza Łukasiewicz
Przemysłowy Instytut Automatyki i Pomiarów PIAP
Al. Jerozolimskie 202, 02-486 Warszawa
next prev parent reply other threads:[~2020-09-14 5:26 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-03 0:06 [PATCH net v2] drivers/net/wan/hdlc_fr: Add needed_headroom for PVC devices Xie He
2020-09-04 22:14 ` Jakub Kicinski
2020-09-05 1:28 ` Xie He
2020-09-05 1:57 ` Xie He
2020-09-05 4:36 ` Jakub Kicinski
2020-09-05 9:20 ` Xie He
2020-09-14 5:26 ` Krzysztof Hałasa [this message]
2020-09-14 6:18 ` Xie He
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=m3v9ghgc97.fsf@t19.piap.pl \
--to=khalasa@piap.pl \
--cc=davem@davemloft.net \
--cc=khc@pm.waw.pl \
--cc=kuba@kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=ms@dev.tdt.de \
--cc=netdev@vger.kernel.org \
--cc=willemdebruijn.kernel@gmail.com \
--cc=xie.he.0141@gmail.com \
/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).