Date: Fri, 8 Mar 2013 23:26:15 GMT From: Keith Reynolds <keith.reynolds@tidalscale.com> To: freebsd-gnats-submit@FreeBSD.org Subject: misc/176771: user-mode netgraph node hangs when replying to control message Message-ID: <201303082326.r28NQF69063317@red.freebsd.org> Resent-Message-ID: <201303082330.r28NU0E5079252@freefall.freebsd.org>
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>Number: 176771
>Category: misc
>Synopsis: user-mode netgraph node hangs when replying to control message
>Confidential: no
>Severity: non-critical
>Priority: low
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Fri Mar 08 23:30:00 UTC 2013
>Closed-Date:
>Last-Modified:
>Originator: Keith Reynolds
>Release: 10.0-CURRENT
>Organization:
TidalScale
>Environment:
FreeBSD ts_bhyve1.local 10.0-CURRENT FreeBSD 10.0-CURRENT #1 r245569: Tue Mar 5 14:24:01 PST 2013 root@ts_bhyve1.local:/usr/obj/usr/src/sys/TS amd64
>Description:
When a netgraph client calls NgSendReplyMsg() to reply to a netgraph control message that is marked as having a reply (msg->header.cmd & NGM_HASREPLY), the library blocks waiting for a reply that will never come, because the message that's being sent *IS* the reply. It doesn't account for the possibility that the user-mode client is replying to a netgraph control message rather than originating one.
>How-To-Repeat:
Write a user-mode netgraph client that responds to the NGM_GENERIC_COOKIE/NGM_TEXT_STATUS control message, which is marked as NGM_HASREPLY, and use "ngctl status <node_path>" to query it. The call to NgSendReplyMsg() will block until another control message comes in, which won't happen until you use ngctl to send another request.
>Fix:
See the attached patch to lib/libnetgraph/msg.c. The change checks msg->header.flags & NGF_RESP to determine if the message being sent is the expected reply before blocking to wait for one.
Patch attached with submission follows:
Index: msg.c
===================================================================
--- msg.c (revision 245569)
+++ msg.c (working copy)
@@ -234,7 +234,7 @@
}
/* Wait for reply if there should be one. */
- if (msg->header.cmd & NGM_HASREPLY) {
+ if (msg->header.cmd & NGM_HASREPLY && !(msg->header.flags & NGF_RESP)) {
struct pollfd rfds;
int n;
>Release-Note:
>Audit-Trail:
>Unformatted:
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