Date: Tue, 21 Apr 2009 22:43:32 +0000 (UTC) From: Robert Watson <rwatson@FreeBSD.org> To: cvs-src-old@freebsd.org Subject: cvs commit: src/sys/net if.c if_mib.c if_var.h Message-ID: <200904212243.n3LMhj3W094191@repoman.freebsd.org>
next in thread | raw e-mail | index | archive | help
rwatson 2009-04-21 22:43:32 UTC
FreeBSD src repository
Modified files:
sys/net if.c if_mib.c if_var.h
Log:
SVN rev 191367 on 2009-04-21 22:43:32Z by rwatson
Start to address a number of races relating to use of ifnet pointers
after the corresponding interface has been destroyed:
(1) Add an ifnet refcount, ifp->if_refcount. Initialize it to 1 in
if_alloc(), and modify if_free_type() to decrement and check the
refcount.
(2) Add new if_ref() and if_rele() interfaces to allow kernel code
walking global interface lists to release IFNET_[RW]LOCK() yet
keep the ifnet stable. Currently, if_rele() is a no-op wrapper
around if_free(), but this may change in the future.
(3) Add new ifnet field, if_alloctype, which caches the type passed
to if_alloc(), but unlike if_type, won't be changed by drivers.
This allows asynchronous free's of the interface after the
driver has released it to still use the right type. Use that
instead of the type passed to if_free_type(), but assert that
they are the same (might have to rethink this if that doesn't
work out).
(4) Add a new ifnet_byindex_ref(), which looks up an interface by
index and returns a reference rather than a pointer to it.
(5) Fix if_alloc() to fully initialize the if_addr_mtx before hooking
up the ifnet to global lists.
(6) Modify sysctls in if_mib.c to use ifnet_byindex_ref() and release
the ifnet when done.
When this change is MFC'd, it will need to replace if_ispare fields
rather than adding new fields in order to avoid breaking the binary
interface. Once this change is MFC'd, if_free_type() should be
removed, as its 'type' argument is now optional.
This refcount is not appropriate for counting mbuf pkthdr references,
and also not for counting entry into the device driver via ifnet
function pointers. An rmlock may be appropriate for the latter.
Rather, this is about ensuring data structure stability when reaching
an ifnet via global ifnet lists and tables followed by copy in or out
of userspace.
MFC after: 3 weeks
Reported by: mdtancsa
Reviewed by: brooks
Revision Changes Path
1.321 +54 -13 src/sys/net/if.c
1.24 +19 -15 src/sys/net/if_mib.c
1.135 +11 -0 src/sys/net/if_var.h
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?200904212243.n3LMhj3W094191>