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doc: Update TODO.smpnet to reflect invention of ETHER_F_ALLMULTI.

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riastradh 2021-12-31 00:57:12 +00:00
parent d0ff7e426a
commit 34e921e5dc
1 changed files with 6 additions and 10 deletions
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doc/TODO.smpnet
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@ -1,4 +1,4 @@
$NetBSD: TODO.smpnet,v 1.44 2021/08/09 19:24:33 andvar Exp $
$NetBSD: TODO.smpnet,v 1.45 2021/12/31 00:57:12 riastradh Exp $
MP-safe components
==================
@ -261,14 +261,10 @@ avoid performance degradation by lock contentions. Traditionally IFF_RUNNING,
IFF_UP and IFF_OACTIVE flags of if_flags are checked on packet processing. If
you make a driver MP-safe you must remove such checks.
IFF_ALLMULTI can be set/unset via if_mcast_op. To protect updates of the flag,
we had added IFNET_LOCK around if_mcast_op. However that was not a good
approach because if_mcast_op is typically called in the middle of a call path
and holding IFNET_LOCK such places is problematic. Actually a deadlock is
observed. Probably we should remove IFNET_LOCK and manage IFF_ALLMULTI
somewhere other than if_flags, for example ethercom or driver itself (or a
common driver framework once it appears). Such a change is feasible because
IFF_ALLMULTI is only set/unset by a driver and not accessed from any common
components such as network protocols.
Drivers should not touch IFF_ALLMULTI. They are tempted to do so when updating
hardware multicast filters on SIOCADDMULTI/SIOCDELMULTI. Instead, they should
use the ETHER_F_ALLMULTI bit in struct ethercom::ec_flags, under ETHER_LOCK.
ether_ioctl takes care of presenting IFF_ALLMULTI according to the current state
of ETHER_F_ALLMULTI when queried with SIOCGIFFLAGS.
Also IFF_PROMISC is checked in ether_input and we should get rid of it somehow.