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Date:      Thu, 26 Jan 2017 01:24:05 +0000 (UTC)
From:      Cy Schubert <cy@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r312787 - in head: contrib/ipfilter/lib sys/contrib/ipfilter/netinet
Message-ID:  <201701260124.v0Q1O5Bc015101@repo.freebsd.org>
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Author: cy
Date: Thu Jan 26 01:24:05 2017
New Revision: 312787
URL: https://svnweb.freebsd.org/changeset/base/312787

Log:
  Currently the fragment info is placed at the top of the linked list
  under a shared read lock. This patch attempts to upgrade the lock to
  an exclusive write lock. If the exclusive write lock fails to be
  obtained, the current fragment is not placed at the head of the list.
  
  This portion of the patch was inspired by NetBSD ip_frag.c r1.4 (which
  effectively removed the section of code that performed the reordering).
  
  The patch to sys/contrib/ipfilter/netinet/ip_compat.h adds the
  MUTEX_TRY_UPGRADE macro to support the patch to ip_frag.c.
  
  The patch to contrib/ipfilter/lib/rwlock_emul.c supports this patch
  by emulating the mutex in userspace when exercised by ipftest(1).
  
  Inspired by:	NetBSD ip_frag.c r1.4
  MFC after:	1 month

Modified:
  head/contrib/ipfilter/lib/rwlock_emul.c
  head/sys/contrib/ipfilter/netinet/ip_compat.h
  head/sys/contrib/ipfilter/netinet/ip_frag.c

Modified: head/contrib/ipfilter/lib/rwlock_emul.c
==============================================================================
--- head/contrib/ipfilter/lib/rwlock_emul.c	Wed Jan 25 23:12:03 2017	(r312786)
+++ head/contrib/ipfilter/lib/rwlock_emul.c	Thu Jan 26 01:24:05 2017	(r312787)
@@ -56,6 +56,27 @@ void eMrwlock_write_enter(rw, file, line
 }
 
 
+void eMrwlock_try_upgrade(rw, file, line)
+	eMrwlock_t *rw;
+	char *file;
+	int line;
+{
+	if (rw->eMrw_magic != EMM_MAGIC) {
+		fprintf(stderr, "%s:eMrwlock_write_enter(%p): bad magic: %#x\n",
+			rw->eMrw_owner, rw, rw->eMrw_magic);
+		abort();
+	}
+	if (rw->eMrw_read != 0 || rw->eMrw_write != 0) {
+		fprintf(stderr,
+			"%s:eMrwlock_try_upgrade(%p): already locked: %d/%d\n",
+			rw->eMrw_owner, rw, rw->eMrw_read, rw->eMrw_write);
+		abort();
+	}
+	rw->eMrw_write++;
+	rw->eMrw_heldin = file;
+	rw->eMrw_heldat = line;
+}
+
 void eMrwlock_downgrade(rw, file, line)
 	eMrwlock_t *rw;
 	char *file;

Modified: head/sys/contrib/ipfilter/netinet/ip_compat.h
==============================================================================
--- head/sys/contrib/ipfilter/netinet/ip_compat.h	Wed Jan 25 23:12:03 2017	(r312786)
+++ head/sys/contrib/ipfilter/netinet/ip_compat.h	Thu Jan 26 01:24:05 2017	(r312787)
@@ -165,6 +165,7 @@ struct  ether_addr {
 #    define	READ_ENTER(x)		rw_rlock(&(x)->ipf_lk)
 #    define	WRITE_ENTER(x)		rw_wlock(&(x)->ipf_lk)
 #    define	MUTEX_DOWNGRADE(x)	rw_downgrade(&(x)->ipf_lk)
+#    define	MUTEX_TRY_UPGRADE(x)	rw_try_upgrade(&(x)->ipf_lk)
 #    define	RWLOCK_INIT(x,y)	rw_init(&(x)->ipf_lk, (y))
 #    define	RW_DESTROY(x)		rw_destroy(&(x)->ipf_lk)
 #    define	RWLOCK_EXIT(x)		do { \
@@ -421,6 +422,8 @@ extern	void	freembt __P((mb_t *));
 
 # define	MUTEX_DOWNGRADE(x)	eMrwlock_downgrade(&(x)->ipf_emu, \
 							   __FILE__, __LINE__)
+# define	MUTEX_TRY_UPGRADE(x)	eMrwlock_try_upgrade(&(x)->ipf_emu, \
+							   __FILE__, __LINE__)
 # define	READ_ENTER(x)		eMrwlock_read_enter(&(x)->ipf_emu, \
 							    __FILE__, __LINE__)
 # define	RWLOCK_INIT(x, y)	eMrwlock_init(&(x)->ipf_emu, y)
@@ -671,6 +674,7 @@ extern	char	*ipf_getifname __P((struct i
 # define	READ_ENTER(x)		;
 # define	WRITE_ENTER(x)		;
 # define	MUTEX_DOWNGRADE(x)	;
+# define	MUTEX_TRY_UPGRADE(x)	;
 # define	RWLOCK_INIT(x, y)	;
 # define	RWLOCK_EXIT(x)		;
 # define	RW_DESTROY(x)		;

Modified: head/sys/contrib/ipfilter/netinet/ip_frag.c
==============================================================================
--- head/sys/contrib/ipfilter/netinet/ip_frag.c	Wed Jan 25 23:12:03 2017	(r312786)
+++ head/sys/contrib/ipfilter/netinet/ip_frag.c	Thu Jan 26 01:24:05 2017	(r312787)
@@ -745,7 +745,7 @@ ipf_frag_lookup(softc, softf, fin, table
 			} else if (off == 0)
 				f->ipfr_seen0 = 1;
 
-			if (f != table[idx]) {
+			if (f != table[idx] && MUTEX_TRY_UPGRADE(lock)) {
 				ipfr_t **fp;
 
 				/*
@@ -763,6 +763,7 @@ ipf_frag_lookup(softc, softf, fin, table
 				table[idx]->ipfr_hprev = &f->ipfr_hnext;
 				f->ipfr_hprev = table + idx;
 				table[idx] = f;
+				MUTEX_DOWNGRADE(lock);
 			}
 
 			/*

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