Date: Wed, 19 Sep 2012 14:16:17 -0700 From: Maksim Yevmenkin <maksim.yevmenkin@gmail.com> To: FreeBSD Current <freebsd-current@freebsd.org> Cc: Scott Long <scottl@freebsd.org> Subject: [RFC] how to get real ifi_baudrate from network interface Message-ID: <CAFPOs6oCot3Bt8S9KUoC-cELw5reP5jmwWnwxS21h=Zq3Q0d-A@mail.gmail.com>
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hello,
for sometime now i've been repeatedly annoyed by the fact that 10G
interfaces lie about their ifi_baudrate. i would like to propose
simple (hopefuly) change to address this.
quick summary of the problem:
struct if_data {
...
u_char ifi_spare_char1; /* spare byte */
u_char ifi_spare_char2; /* spare byte */
...
u_long ifi_baudrate; /* linespeed */
...
};
as you can see ifi_baudrate is an u_long which is an arch specific
type. on 32-bit arch it does not have enough bits to hold 10G line
speed value (in bits per second)
proposal
we reuse one of the ifi_spare_char1 or ifi_spare_char2 bytes and
re-purpose it as power factor to be applied to ifi_baudrate, i.e.
real_ifi_baudrate = ifi_baudrate * 10 ** ifi_spare_char1
obviously, 10G nic drivers will have to set ifi_spare_char1 to
appropriate value, but it should not be a big deal. also, legacy tools
that do not know about ifi_spare_char1 would continue to report
"wrong" ifi_baudrate as they used to.
any objections?
thanks,
max
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