netdev - Re: [PATCH v4 5/7] ipv6 addrconf: implement RFC7559 router solicitation backoff

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Date:   Tue, 27 Sep 2016 18:42:17 +0900
From:   Maciej Żenczykowski <maze@...gle.com>
To:     Hannes Frederic Sowa <hannes@...essinduktion.org>
Cc:     "David S . Miller" <davem@...emloft.net>,
        Linux NetDev <netdev@...r.kernel.org>,
        Erik Kline <ek@...gle.com>,
        Lorenzo Colitti <lorenzo@...gle.com>
Subject: Re: [PATCH v4 5/7] ipv6 addrconf: implement RFC7559 router
 solicitation backoff

> Please just use do_div here and go back to the first version of the
> patch. Variable names could be more aligned with the RFC maybe?

So I tried:

static inline s32 rfc3315_s14_backoff_init(s32 irt)
 {
       /* multiply 'initial retransmission time' by 0.9 .. 1.1 */
       u64 tmp = (900000 + prandom_u32() % 200001) * (u64)irt;
       do_div(tmp, 1000000);
       return (s32)tmp;
 }

static inline s32 rfc3315_s14_backoff_update(s32 rt, s32 mrt)
 {
       /* multiply 'retransmission timeout' by 1.9 .. 2.1 */
       u64 tmp = (1900000 + prandom_u32() % 200001) * (u64)rt;
       do_div(tmp, 1000000);
       if ((s32)tmp > mrt) {
               /* multiply 'maximum retransmission time' by 0.9 .. 1.1 */
               tmp = (900000 + prandom_u32() % 200001) * (u64)mrt;
               do_div(tmp, 1000000);
        }
       return (s32)tmp;
}

but then building for i386 I get:

ERROR: "__udivdi3" [net/netfilter/xt_hashlimit.ko] undefined!

which happens even at net-next/master itself.

Anyway, I'll resubmit assuming the above is what you're looking for...