Re: [PATCH] rtnetlink.7: Document struct ifa_cacheinfo

Alejandro Colomar
2024-11-05T11:33:51Z

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Hi Alex, Kuniyuki, Branden,

On Mon, Nov 04, 2024 at 09:53:38PM GMT, Kuniyuki Iwashima wrote:
> From: Alex Henrie <alexhenrie24@gmail.com>
> Date: Mon, 4 Nov 2024 21:14:20 -0700
> > struct ifa_cacheinfo contains the address's creation time, update time,
> > preferred lifetime, and valid lifetime. See

We use two spaces after period (the correct amount). :)
(I'm thinking we probably want to document something about it in
man-pages(7). Branden, do you want to send a patch about it? I want
to include the references you showed to me, and you probably remember
better those links.)

> > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/uapi/linux/if_addr.h?h=v6.11#n60

Please use this format for links:

Link: <http://example.com>

> >
> > Signed-off-by: Alex Henrie <alexhenrie24@gmail.com>
> > ---
> > man/man7/rtnetlink.7 | 10 +++++++++-
> > 1 file changed, 9 insertions(+), 1 deletion(-)
> >
> > diff --git a/man/man7/rtnetlink.7 b/man/man7/rtnetlink.7
> > index 86ed459bb..b05654315 100644
> > --- a/man/man7/rtnetlink.7
> > +++ b/man/man7/rtnetlink.7
> > @@ -176,7 +176,15 @@ IFA_BROADCAST:raw protocol address:broadcast address
> > IFA_ANYCAST:raw protocol address:anycast address
> > IFA_CACHEINFO:struct ifa_cacheinfo:Address information
> > .TE
> > -.\" FIXME Document struct ifa_cacheinfo
> > +.IP
> > +.EX

Which include provides the structure?

> > +struct ifa_cacheinfo {
> > + __u32 ifa_prefered; /* Preferred lifetime in seconds, -1 = forever */
> > + __u32 ifa_valid; /* Valid lifetime in seconds, -1 = forever */
>
> -1 should be rather 0xFFFFFFFF (INFINITY_LIFE_TIME) as it's unsigned.

I prefer UINT32_MAX over 0xF...F, which might be unclear how many Fs it
has.

> Also, it would be nice to mention that ifa_prefered must be less than
> or equal to ifa_valid (ifa_prefered <= ifa_valid) and 0 is invalid for
> ifa_valid.
>
> 0 <= ifa_prefered <= ifa_valid
> 0 < ifa_valid <= 0xFFFFFFFF

You may want to use interval notation, like we do in timespec(3type).

struct timespec {
time_t tv_sec; /* Seconds */
/* ... */ tv_nsec; /* Nanoseconds [0, 999'999'999] */
};

It might also be interesting to add a separate manual page for the type,
and reference it here. Otherwise, the page starts getting fatty.

Have a lovely day!
Alex

>
>
> > + __u32 cstamp; /* Creation timestamp in hundredths of seconds */
> > + __u32 tstamp; /* Update timestamp in hundredths of seconds */
> > +};
>
> Maybe the explanation can follow the struct here as sentences.
>
>
> > +.EE
> > .TP
> > .B RTM_NEWROUTE
> > .TQ
> > --
> > 2.47.0
>

--
<https://www.alejandro-colomar.es/>