Module Name: src
Committed By: pooka
Date: Wed Apr 14 13:31:33 UTC 2010
Modified Files:
src/sys/net: bpf.c
Log Message:
Add a little comment on how bpf can be made unloadable, per pointer from ad.
To generate a diff of this commit:
cvs rdiff -u -r1.157 -r1.158 src/sys/net/bpf.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/net/bpf.c
diff -u src/sys/net/bpf.c:1.157 src/sys/net/bpf.c:1.158
--- src/sys/net/bpf.c:1.157 Mon Apr 5 07:22:22 2010
+++ src/sys/net/bpf.c Wed Apr 14 13:31:33 2010
@@ -1,4 +1,4 @@
-/* $NetBSD: bpf.c,v 1.157 2010/04/05 07:22:22 joerg Exp $ */
+/* $NetBSD: bpf.c,v 1.158 2010/04/14 13:31:33 pooka Exp $ */
/*
* Copyright (c) 1990, 1991, 1993
@@ -39,7 +39,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: bpf.c,v 1.157 2010/04/05 07:22:22 joerg Exp $");
+__KERNEL_RCSID(0, "$NetBSD: bpf.c,v 1.158 2010/04/14 13:31:33 pooka Exp $");
#if defined(_KERNEL_OPT)
#include "opt_bpf.h"
@@ -1976,8 +1976,24 @@
case MODULE_CMD_FINI:
/*
- * bpf_ops is not (yet) referenced in the callers before
- * attach. maybe other issues too. "safety first".
+ * While there is no reference counting for bpf callers,
+ * unload could at least in theory be done similarly to
+ * system call disestablishment. This should even be
+ * a little simpler:
+ *
+ * 1) replace op vector with stubs
+ * 2) post update to all cpus with xc
+ * 3) check that nobody is in bpf anymore
+ * (it's doubtful we'd want something like l_sysent,
+ * but we could do something like *signed* percpu
+ * counters. if the sum is 0, we're good).
+ * 4) if fail, unroll changes
+ *
+ * NOTE: change won't be atomic to the outside. some
+ * packets may be not captured even if unload is
+ * not succesful. I think packet capture not working
+ * is a perfectly logical consequence of trying to
+ * disable packet capture.
*/
error = EOPNOTSUPP;
break;
