Module Name:    src
Committed By:   rmind
Date:           Sun Sep 29 17:00:29 UTC 2019

Modified Files:
        src/sys/net/npf: npf_conn.c npf_if.c npf_impl.h npf_ruleset.c

Log Message:
NPF ifmap: rework and fix a few small bugs.


To generate a diff of this commit:
cvs rdiff -u -r1.29 -r1.30 src/sys/net/npf/npf_conn.c
cvs rdiff -u -r1.10 -r1.11 src/sys/net/npf/npf_if.c
cvs rdiff -u -r1.79 -r1.80 src/sys/net/npf/npf_impl.h
cvs rdiff -u -r1.48 -r1.49 src/sys/net/npf/npf_ruleset.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/npf/npf_conn.c
diff -u src/sys/net/npf/npf_conn.c:1.29 src/sys/net/npf/npf_conn.c:1.30
--- src/sys/net/npf/npf_conn.c:1.29	Tue Aug  6 11:40:15 2019
+++ src/sys/net/npf/npf_conn.c	Sun Sep 29 17:00:29 2019
@@ -107,7 +107,7 @@
 
 #ifdef _KERNEL
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: npf_conn.c,v 1.29 2019/08/06 11:40:15 christos Exp $");
+__KERNEL_RCSID(0, "$NetBSD: npf_conn.c,v 1.30 2019/09/29 17:00:29 rmind Exp $");
 
 #include <sys/param.h>
 #include <sys/types.h>
@@ -782,7 +782,8 @@ npf_conn_export(npf_t *npf, npf_conn_t *
 	nvlist_add_number(cdict, "flags", con->c_flags);
 	nvlist_add_number(cdict, "proto", con->c_proto);
 	if (con->c_ifid) {
-		const char *ifname = npf_ifmap_getname(npf, con->c_ifid);
+		char ifname[IFNAMSIZ];
+		npf_ifmap_copyname(npf, con->c_ifid, ifname, sizeof(ifname));
 		nvlist_add_string(cdict, "ifname", ifname);
 	}
 	nvlist_add_binary(cdict, "state", &con->c_state, sizeof(npf_state_t));

Index: src/sys/net/npf/npf_if.c
diff -u src/sys/net/npf/npf_if.c:1.10 src/sys/net/npf/npf_if.c:1.11
--- src/sys/net/npf/npf_if.c:1.10	Sun Aug 11 20:26:33 2019
+++ src/sys/net/npf/npf_if.c	Sun Sep 29 17:00:29 2019
@@ -1,4 +1,5 @@
 /*-
+ * Copyright (c) 2019 Mindaugas Rasiukevicius <rmind at noxt eu>
  * Copyright (c) 2013 The NetBSD Foundation, Inc.
  * All rights reserved.
  *
@@ -28,23 +29,34 @@
  */
 
 /*
- * NPF network interface handling module.
+ * NPF network interface handling.
  *
- * NPF uses its own interface IDs (npf-if-id).  When NPF configuration is
- * (re)loaded, each required interface name is registered and a matching
- * network interface gets an ID assigned.  If an interface is not present,
- * it gets an ID on attach.
+ * NPF uses its own interface IDs (npf-if-id).  These IDs start from 1.
+ * Zero is reserved to indicate "no interface" case or an interface of
+ * no interest (i.e. not registered).
  *
- * IDs start from 1.  Zero is reserved to indicate "no interface" case or
- * an interface of no interest (i.e. not registered).
+ * This module provides an interface to primarily handle the following:
  *
- * The IDs are mapped synchronously based on interface events which are
- * monitored using pfil(9) hooks.
+ * - Bind a symbolic interface name to NPF interface ID.
+ * - Associate NPF interface ID when the network interface is attached.
+ *
+ * When NPF configuration is (re)loaded, each referenced network interface
+ * name is registered with a unique ID.  If the network interface is already
+ * attached, then the ID is associated with it immediately; otherwise, IDs
+ * are associated/disassociated on interface events which are monitored
+ * using pfil(9) hooks.
+ *
+ * To avoid race conditions when an active NPF configuration is updated or
+ * interfaces are detached/attached, the interface names are never removed
+ * and therefore IDs are never re-assigned.  The only point when interface
+ * names and IDs are cleared is when the configuration is flushed.
+ *
+ * A linear counter is used for IDs.
  */
 
 #ifdef _KERNEL
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: npf_if.c,v 1.10 2019/08/11 20:26:33 rmind Exp $");
+__KERNEL_RCSID(0, "$NetBSD: npf_if.c,v 1.11 2019/09/29 17:00:29 rmind Exp $");
 
 #include <sys/param.h>
 #include <sys/types.h>
@@ -55,9 +67,13 @@ __KERNEL_RCSID(0, "$NetBSD: npf_if.c,v 1
 #include "npf_impl.h"
 
 typedef struct npf_ifmap {
-	char		n_ifname[IFNAMSIZ];
+	char		ifname[IFNAMSIZ + 1];
 } npf_ifmap_t;
 
+#define	NPF_IFMAP_NOID			(0U)
+#define	NPF_IFMAP_SLOT2ID(npf, slot)	((npf)->ifmap_off + (slot) + 1)
+#define	NPF_IFMAP_ID2SLOT(npf, id)	((id) - (npf)->ifmap_off - 1)
+
 void
 npf_ifmap_init(npf_t *npf, const npf_ifops_t *ifops)
 {
@@ -66,8 +82,10 @@ npf_ifmap_init(npf_t *npf, const npf_ifo
 	KASSERT(ifops != NULL);
 	ifops->flush((void *)(uintptr_t)0);
 
+	mutex_init(&npf->ifmap_lock, MUTEX_DEFAULT, IPL_SOFTNET);
 	npf->ifmap = kmem_zalloc(nbytes, KM_SLEEP);
 	npf->ifmap_cnt = 0;
+	npf->ifmap_off = 0;
 	npf->ifops = ifops;
 }
 
@@ -75,82 +93,101 @@ void
 npf_ifmap_fini(npf_t *npf)
 {
 	const size_t nbytes = sizeof(npf_ifmap_t) * NPF_MAX_IFMAP;
+	mutex_destroy(&npf->ifmap_lock);
 	kmem_free(npf->ifmap, nbytes);
 }
 
-static u_int
-npf_ifmap_new(npf_t *npf)
-{
-	KASSERT(npf_config_locked_p(npf));
-
-	for (u_int i = 0; i < npf->ifmap_cnt; i++)
-		if (npf->ifmap[i].n_ifname[0] == '\0')
-			return i + 1;
-
-	if (npf->ifmap_cnt == NPF_MAX_IFMAP) {
-		printf("npf_ifmap_new: out of slots; bump NPF_MAX_IFMAP\n");
-		return 0;
-	}
-	return ++npf->ifmap_cnt;
-}
-
-static u_int
+static unsigned
 npf_ifmap_lookup(npf_t *npf, const char *ifname)
 {
-	KASSERT(npf_config_locked_p(npf));
+	KASSERT(mutex_owned(&npf->ifmap_lock));
 
-	for (u_int i = 0; i < npf->ifmap_cnt; i++) {
-		npf_ifmap_t *nim = &npf->ifmap[i];
+	for (unsigned i = 0; i < npf->ifmap_cnt; i++) {
+		npf_ifmap_t *ifmap = &npf->ifmap[i];
 
-		if (nim->n_ifname[0] && strcmp(nim->n_ifname, ifname) == 0)
-			return i + 1;
+		if (strcmp(ifmap->ifname, ifname) == 0) {
+			return NPF_IFMAP_SLOT2ID(npf, i);
+		}
 	}
-	return 0;
+	return NPF_IFMAP_NOID;
 }
 
-u_int
+/*
+ * npf_ifmap_register: register an interface name; return an assigned
+ * NPF network ID on success (non-zero).
+ *
+ * This routine is mostly called on NPF configuration (re)load for the
+ * interfaces names referenced by the rules.
+ */
+unsigned
 npf_ifmap_register(npf_t *npf, const char *ifname)
 {
-	npf_ifmap_t *nim;
+	npf_ifmap_t *ifmap;
+	unsigned id, i;
 	ifnet_t *ifp;
-	u_int i;
 
-	npf_config_enter(npf);
-	if ((i = npf_ifmap_lookup(npf, ifname)) != 0) {
+	mutex_enter(&npf->ifmap_lock);
+	if ((id = npf_ifmap_lookup(npf, ifname)) != NPF_IFMAP_NOID) {
 		goto out;
 	}
-	if ((i = npf_ifmap_new(npf)) == 0) {
+	if (npf->ifmap_cnt == NPF_MAX_IFMAP) {
+		printf("npf_ifmap_new: out of slots; bump NPF_MAX_IFMAP\n");
+		id = NPF_IFMAP_NOID;
 		goto out;
 	}
-	nim = &npf->ifmap[i - 1];
-	strlcpy(nim->n_ifname, ifname, IFNAMSIZ);
+	KASSERT(npf->ifmap_cnt < NPF_MAX_IFMAP);
+
+	/* Allocate a new slot and convert and assign an ID. */
+	i = npf->ifmap_cnt++;
+	ifmap = &npf->ifmap[i];
+	strlcpy(ifmap->ifname, ifname, IFNAMSIZ);
+	id = NPF_IFMAP_SLOT2ID(npf, i);
 
 	if ((ifp = npf->ifops->lookup(ifname)) != NULL) {
-		npf->ifops->setmeta(ifp, (void *)(uintptr_t)i);
+		npf->ifops->setmeta(ifp, (void *)(uintptr_t)id);
 	}
 out:
-	npf_config_exit(npf);
-	return i;
+	mutex_exit(&npf->ifmap_lock);
+	return id;
 }
 
 void
 npf_ifmap_flush(npf_t *npf)
 {
-	KASSERT(npf_config_locked_p(npf));
-
-	for (u_int i = 0; i < npf->ifmap_cnt; i++) {
-		npf->ifmap[i].n_ifname[0] = '\0';
+	mutex_enter(&npf->ifmap_lock);
+	npf->ifops->flush((void *)(uintptr_t)NPF_IFMAP_NOID);
+	for (unsigned i = 0; i < npf->ifmap_cnt; i++) {
+		npf->ifmap[i].ifname[0] = '\0';
 	}
 	npf->ifmap_cnt = 0;
-	npf->ifops->flush((void *)(uintptr_t)0);
+
+	/*
+	 * Reset the ID counter if reaching the overflow; this is not
+	 * realistic, but we maintain correctness.
+	 */
+	if (npf->ifmap_off < (UINT_MAX - NPF_MAX_IFMAP)) {
+		npf->ifmap_off += NPF_MAX_IFMAP;
+	} else {
+		npf->ifmap_off = 0;
+	}
+	mutex_exit(&npf->ifmap_lock);
 }
 
-u_int
+/*
+ * npf_ifmap_getid: get the ID for the given network interface.
+ *
+ * => This routine is typically called from the packet handler when
+ *    matching whether the packet is on particular network interface.
+ *
+ * => This routine is lock-free; if the NPF configuration is flushed
+ *    while the packet is in-flight, the ID will not match because we
+ *    keep the IDs linear.
+ */
+unsigned
 npf_ifmap_getid(npf_t *npf, const ifnet_t *ifp)
 {
-	const u_int i = (uintptr_t)npf->ifops->getmeta(ifp);
-	KASSERT(i <= npf->ifmap_cnt);
-	return i;
+	const unsigned id = (uintptr_t)npf->ifops->getmeta(ifp);
+	return id;
 }
 
 /*
@@ -158,45 +195,47 @@ npf_ifmap_getid(npf_t *npf, const ifnet_
  * lock, but it is only used temporarily and only for logging.
  */
 void
-npf_ifmap_copyname(npf_t *npf, u_int id, char *buf, size_t len)
+npf_ifmap_copylogname(npf_t *npf, unsigned id, char *buf, size_t len)
 {
-	if (id > 0 && id < npf->ifmap_cnt)
-		strlcpy(buf, npf->ifmap[id - 1].n_ifname,
-		    MIN(len, sizeof(npf->ifmap[id - 1].n_ifname)));
-	else
+	if (id != NPF_IFMAP_NOID) {
+		const unsigned i = NPF_IFMAP_ID2SLOT(npf, id);
+		npf_ifmap_t *ifmap = &npf->ifmap[i];
+
+		/*
+		 * Lock-free access is safe as there is an extra byte
+		 * with a permanent NUL terminator at the end.
+		 */
+		strlcpy(buf, ifmap->ifname, MIN(len, IFNAMSIZ));
+	} else {
 		strlcpy(buf, "???", len);
+	}
 }
 
-const char *
-npf_ifmap_getname(npf_t *npf, const u_int id)
+void
+npf_ifmap_copyname(npf_t *npf, unsigned id, char *buf, size_t len)
 {
-	const char *ifname;
-
-	KASSERT(npf_config_locked_p(npf));
-	KASSERT(id > 0 && id <= npf->ifmap_cnt);
-
-	ifname = npf->ifmap[id - 1].n_ifname;
-	KASSERT(ifname[0] != '\0');
-	return ifname;
+	mutex_enter(&npf->ifmap_lock);
+	npf_ifmap_copylogname(npf, id, buf, len);
+	mutex_exit(&npf->ifmap_lock);
 }
 
 __dso_public void
 npfk_ifmap_attach(npf_t *npf, ifnet_t *ifp)
 {
 	const npf_ifops_t *ifops = npf->ifops;
-	u_int i;
+	unsigned id;
 
-	npf_config_enter(npf);
-	i = npf_ifmap_lookup(npf, ifops->getname(ifp));
-	ifops->setmeta(ifp, (void *)(uintptr_t)i);
-	npf_config_exit(npf);
+	mutex_enter(&npf->ifmap_lock);
+	id = npf_ifmap_lookup(npf, ifops->getname(ifp));
+	ifops->setmeta(ifp, (void *)(uintptr_t)id);
+	mutex_exit(&npf->ifmap_lock);
 }
 
 __dso_public void
 npfk_ifmap_detach(npf_t *npf, ifnet_t *ifp)
 {
 	/* Diagnostic. */
-	npf_config_enter(npf);
-	npf->ifops->setmeta(ifp, (void *)(uintptr_t)0);
-	npf_config_exit(npf);
+	mutex_enter(&npf->ifmap_lock);
+	npf->ifops->setmeta(ifp, (void *)(uintptr_t)NPF_IFMAP_NOID);
+	mutex_exit(&npf->ifmap_lock);
 }

Index: src/sys/net/npf/npf_impl.h
diff -u src/sys/net/npf/npf_impl.h:1.79 src/sys/net/npf/npf_impl.h:1.80
--- src/sys/net/npf/npf_impl.h:1.79	Sun Aug 25 17:38:25 2019
+++ src/sys/net/npf/npf_impl.h	Sun Sep 29 17:00:29 2019
@@ -234,6 +234,8 @@ struct npf {
 	const npf_ifops_t *	ifops;
 	struct npf_ifmap *	ifmap;
 	unsigned		ifmap_cnt;
+	unsigned		ifmap_off;
+	kmutex_t		ifmap_lock;
 
 	/* Associated worker thread. */
 	unsigned		worker_id;
@@ -319,8 +321,8 @@ void		npf_ifmap_fini(npf_t *);
 u_int		npf_ifmap_register(npf_t *, const char *);
 void		npf_ifmap_flush(npf_t *);
 u_int		npf_ifmap_getid(npf_t *, const ifnet_t *);
-const char *	npf_ifmap_getname(npf_t *, const u_int);
-void		npf_ifmap_copyname(npf_t *, u_int, char *, size_t);
+void		npf_ifmap_copylogname(npf_t *, unsigned, char *, size_t);
+void		npf_ifmap_copyname(npf_t *, unsigned, char *, size_t);
 
 void		npf_ifaddr_sync(npf_t *, ifnet_t *);
 void		npf_ifaddr_flush(npf_t *, ifnet_t *);

Index: src/sys/net/npf/npf_ruleset.c
diff -u src/sys/net/npf/npf_ruleset.c:1.48 src/sys/net/npf/npf_ruleset.c:1.49
--- src/sys/net/npf/npf_ruleset.c:1.48	Tue Jul 23 00:52:01 2019
+++ src/sys/net/npf/npf_ruleset.c	Sun Sep 29 17:00:29 2019
@@ -33,7 +33,7 @@
 
 #ifdef _KERNEL
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: npf_ruleset.c,v 1.48 2019/07/23 00:52:01 rmind Exp $");
+__KERNEL_RCSID(0, "$NetBSD: npf_ruleset.c,v 1.49 2019/09/29 17:00:29 rmind Exp $");
 
 #include <sys/param.h>
 #include <sys/types.h>
@@ -680,7 +680,8 @@ npf_rule_export(npf_t *npf, const npf_ru
 		nvlist_add_binary(rule, "code", rl->r_code, rl->r_clen);
 	}
 	if (rl->r_ifid) {
-		const char *ifname = npf_ifmap_getname(npf, rl->r_ifid);
+		char ifname[IFNAMSIZ];
+		npf_ifmap_copyname(npf, rl->r_ifid, ifname, sizeof(ifname));
 		nvlist_add_string(rule, "ifname", ifname);
 	}
 	nvlist_add_number(rule, "id", rl->r_id);

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