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Add a note to the man page warning users about possible lock order

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reversals+system lock ups if they are using ucred based rules
while running with debug.mpsafenet=1.

I am working on merging a shared locking mechanism into ipfw which
should take care of this problem, but it still requires a bit more
testing and review.
This commit is contained in:
Christian S.J. Peron 2004-10-09 20:07:33 +00:00
parent 55fc8c1146
commit 93962a3a50
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=136335
1 changed files with 10 additions and 0 deletions
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sbin/ipfw/ipfw.8
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@ -972,10 +972,14 @@ Matches all TCP or UDP packets sent by or received for a
A
.Ar group
may be specified by name or number.
This option should be used only if debug.mpsafenet=0 to avoid
lock ordering issues which could result in system hard locks.
.It Cm jail Ar prisonID
Matches all TCP or UDP packets sent by or received for the
jail whos prison ID is
.Ar prisonID .
This option should be used only if debug.mpsafenet=0 to avoid
lock ordering issues which could result in system hard locks.
.It Cm icmptypes Ar types
Matches ICMP packets whose ICMP type is in the list
.Ar types .
@ -1300,6 +1304,8 @@ Match all TCP or UDP packets sent by or received for a
A
.Ar user
may be matched by name or identification number.
This option should be used only if debug.mpsafenet=0 to avoid
lock ordering issues which could result in system hard locks.
.It Cm verrevpath
For incoming packets,
a routing table lookup is done on the packet's source address.
@ -2335,6 +2341,10 @@ the sleep terminates thus restoring the previous situation.
.Xr sysctl 8 ,
.Xr syslogd 8
.Sh BUGS
Lock ordering issues could result in system hard locks if rules which
contain UID, GID or jail ID constraints and used with debug.mpsafenet
set to 1.
.Pp
The syntax has grown over the years and sometimes it might be confusing.
Unfortunately, backward compatibility prevents cleaning up mistakes
made in the definition of the syntax.