From 4155069acee2ca62c534d210b130699497a7da31 Mon Sep 17 00:00:00 2001
From: Paul Stewart <pstew@chromium.org>
Date: Mon, 31 May 2021 13:22:06 +0000
Subject: [PATCH 04/19] Allow lease file to be set on command line

Currently, dhcpcd names its lease files using the interface name
as the unique part of the name.  There are a couple reasons why
this may not work well: firstly if "eth0" can have different MAC
addresses (multiple USB-Ethernet dongles for example) leases for
one interface aren't valid for the other.  Secondly, when using
a wireless interface, it would be convenient to hold multiple
leases in parallel for each SSID one is connected to.

This change adds a suffix to each interface argument (dhcpcd can
accept multiple interface arguments) that specifies the identifier
to use to save lease files with.  By default, the behavior is
identical.

The second CL (https://gerrit.chromium.org/gerrit/22170) for fixing
pid file formating bug originally introduced by this CL is not needed
anymore since this bug doesn't exist/apply in the updated implementation.

BUG=chromium-os:25717
TEST=Re-run dhcpcd with and without an identifier suffix.

Note: the implementation has been changed during upgrade to 7.2.5, the
original one has been reviewed at:
Reviewed-on: https://gerrit.chromium.org/gerrit/21991
Reviewed-on: https://gerrit.chromium.org/gerrit/22170
---
 src/dhcp-common.c | 10 +++++-
 src/dhcp.h        |  2 +-
 src/dhcpcd.8.in   |  8 ++++-
 src/dhcpcd.c      | 24 ++++++++------
 src/dhcpcd.h      |  2 ++
 src/if-options.c  |  2 +-
 src/if.c          | 82 ++++++++++++++++++++++++++++++++++++++---------
 src/if.h          |  8 +++++
 8 files changed, 108 insertions(+), 30 deletions(-)

diff --git a/src/dhcp-common.c b/src/dhcp-common.c
index c562ada7..866c3ccb 100644
--- a/src/dhcp-common.c
+++ b/src/dhcp-common.c
@@ -838,6 +838,14 @@ dhcp_set_leasefile(char *leasefile, size_t len, int family,
 		return 0;
 	}
 
+	if (strlen(ifp->lease_identifier) > 0) {
+		/* Only supports lease identifier for IPv4 for now. */
+		if (family == AF_INET) {
+			return snprintf(leasefile, len, LEASEFILE,
+					ifp->lease_identifier, "");
+		}
+	}
+
 	switch (family) {
 	case AF_INET:
 	case AF_INET6:
@@ -1070,7 +1078,7 @@ dhcp_read_lease_fd(int fd, void **lease)
 	size_t sz;
 	void *buf;
 	ssize_t len;
-	
+
 	if (fstat(fd, &st) != 0)
 		goto out;
 	if (!S_ISREG(st.st_mode)) {
diff --git a/src/dhcp.h b/src/dhcp.h
index e54671e1..becf27c2 100644
--- a/src/dhcp.h
+++ b/src/dhcp.h
@@ -230,7 +230,7 @@ struct dhcp_state {
 	struct ipv4_addr *addr;
 	uint8_t added;
 
-	char leasefile[sizeof(LEASEFILE) + IF_NAMESIZE + (IF_SSIDLEN * 4)];
+	char leasefile[PATH_MAX];
 	struct timespec started;
 	unsigned char *clientid;
 	struct authstate auth;
diff --git a/src/dhcpcd.8.in b/src/dhcpcd.8.in
index 8d47dd7f..607df76b 100644
--- a/src/dhcpcd.8.in
+++ b/src/dhcpcd.8.in
@@ -201,6 +201,12 @@ changes the routes to use the interface with the same route and the lowest
 metric.
 See options below for controlling which interfaces we allow and deny through
 the use of patterns.
+.Pp
+If an interface name is suffixed by an equal-sign, the text following the
+equal sign will be used instead of the interface name as the unique identifier
+for the DHCP lease file.  Doing so allows the caller to specify different
+lease files for the same interface (e.g, when switching the same wireless
+interface between different 802.11 networks).
 .Ss Hooking into events
 .Nm
 runs
@@ -821,7 +827,7 @@ Control socket to per interface daemon.
 .Xr dhcpcd-run-hooks 8 ,
 .Xr resolvconf 8
 .Sh STANDARDS
-RFC\ 951, RFC\ 1534, RFC\ 2104, RFC\ 2131, RFC\ 2132, RFC\ 2563, RFC\ 2855, 
+RFC\ 951, RFC\ 1534, RFC\ 2104, RFC\ 2131, RFC\ 2132, RFC\ 2563, RFC\ 2855,
 RFC\ 3004, RFC\ 3118, RFC\ 3203, RFC\ 3315, RFC\ 3361, RFC\ 3633, RFC\ 3396,
 RFC\ 3397, RFC\ 3442, RFC\ 3495, RFC\ 3925, RFC\ 3927, RFC\ 4039, RFC\ 4075,
 RFC\ 4242, RFC\ 4361, RFC\ 4390, RFC\ 4702, RFC\ 4074, RFC\ 4861, RFC\ 4833,
diff --git a/src/dhcpcd.c b/src/dhcpcd.c
index 67dc3d64..7e778338 100644
--- a/src/dhcpcd.c
+++ b/src/dhcpcd.c
@@ -1531,6 +1531,7 @@ main(int argc, char **argv)
 	int sig = 0;
 	const char *siga = NULL;
 #endif
+	char ifn[IF_NAMESIZE];
 
 	/* Test for --help and --version */
 	if (argc > 1) {
@@ -1727,12 +1728,11 @@ printpidfile:
 		 *  instance for that interface. */
 		if (optind == argc - 1 && !(ctx.options & DHCPCD_MASTER)) {
 			const char *per;
-			const char *ifname;
+			const char *ifname = if_namepart(ifn, *ctx.ifv);
 
-			ifname = *ctx.ifv;
-			if (ifname == NULL || strlen(ifname) > IF_NAMESIZE) {
-				errno = ifname == NULL ? EINVAL : E2BIG;
-				logerr("%s: ", ifname);
+			if (ifname == NULL) {
+				errno = EINVAL;
+				logerrx("missing or invalid interface name");
 				goto exit_failure;
 			}
 			/* Allow a dhcpcd interface per address family */
@@ -1811,7 +1811,7 @@ printpidfile:
 				goto exit_failure;
 			}
 			if (optind != argc)
-				strlcpy(ctx.pidfile, argv[optind],
+				strlcpy(ctx.pidfile, if_namepart(ifn, argv[optind]),
 				    sizeof(ctx.pidfile));
 			ifp->ctx = &ctx;
 			TAILQ_INSERT_HEAD(ctx.ifaces, ifp, next);
@@ -1857,7 +1857,8 @@ printpidfile:
 	{
 #endif
 		if (!(ctx.options & DHCPCD_MASTER))
-			ctx.control_fd = control_open(argv[optind]);
+			ctx.control_fd = control_open(
+				if_namepart(ifn, argv[optind]));
 		if (ctx.control_fd == -1)
 			ctx.control_fd = control_open(NULL);
 		if (ctx.control_fd != -1) {
@@ -1937,7 +1938,9 @@ printpidfile:
 	}
 #else
 	if (control_start(&ctx,
-	    ctx.options & DHCPCD_MASTER ? NULL : argv[optind]) == -1)
+			  ctx.options & DHCPCD_MASTER
+			  ? NULL : if_namepart(ifn, argv[optind]))
+	    == -1)
 	{
 		logerr("%s: control_start", __func__);
 		goto exit_failure;
@@ -1949,7 +1952,8 @@ printpidfile:
 
 #ifdef HAVE_SETPROCTITLE
 	setproctitle("%s%s%s",
-	    ctx.options & DHCPCD_MASTER ? "[master]" : argv[optind],
+	    ctx.options & DHCPCD_MASTER ? "[master]"
+					: if_namepart(ifn, argv[optind]),
 	    ctx.options & DHCPCD_IPV4 ? " [ip4]" : "",
 	    ctx.options & DHCPCD_IPV6 ? " [ip6]" : "");
 #endif
@@ -1983,7 +1987,7 @@ printpidfile:
 		if ((ifp = if_find(ctx.ifaces, ctx.ifv[i])) == NULL ||
 		    !ifp->active)
 			logerrx("%s: interface not found or invalid",
-			    ctx.ifv[i]);
+				if_namepart(ifn, ctx.ifv[i]));
 	}
 	TAILQ_FOREACH(ifp, ctx.ifaces, next) {
 		if (ifp->active == IF_ACTIVE_USER)
diff --git a/src/dhcpcd.h b/src/dhcpcd.h
index 3e35a3de..5adafc68 100644
--- a/src/dhcpcd.h
+++ b/src/dhcpcd.h
@@ -44,6 +44,7 @@
 #define IF_SSIDLEN	32
 #define PROFILE_LEN	64
 #define SECRET_LEN	64
+#define LEASE_IDENTIFIER_LEN (PATH_MAX - sizeof(LEASEFILE))
 
 #define IF_INACTIVE	0
 #define IF_ACTIVE	1
@@ -88,6 +89,7 @@ struct interface {
 	bool wireless;
 	uint8_t ssid[IF_SSIDLEN];
 	unsigned int ssid_len;
+        char lease_identifier[LEASE_IDENTIFIER_LEN];
 
 	char profile[PROFILE_LEN];
 	struct if_options *options;
diff --git a/src/if-options.c b/src/if-options.c
index 80d1efda..1ced9642 100644
--- a/src/if-options.c
+++ b/src/if-options.c
@@ -2512,7 +2512,7 @@ read_config(struct dhcpcd_ctx *ctx,
 				skip = 1;
 				continue;
 			}
-			if (ifname && strcmp(line, ifname) == 0)
+			if (ifname && if_namecmp(line, ifname, NULL) == 0)
 				skip = 0;
 			else
 				skip = 1;
diff --git a/src/if.c b/src/if.c
index 28597dc2..643fc546 100644
--- a/src/if.c
+++ b/src/if.c
@@ -72,6 +72,21 @@
 #include "ipv6nd.h"
 #include "logerr.h"
 
+/* This utility function is used to work around case for lease file encoded in
+ * interface name after '='.  If the lease part is not present the 'name'
+ * argument is returned, otherwise the interface part is copied to the 'buf' and
+ * it is returned. */
+const char* if_namepart(char *buf, const char *name)
+{
+	const char *p;
+
+	if (name == NULL || (p = strchr(name, '=')) == NULL)
+		return name;
+
+	strlcpy(buf, name, MIN(IF_NAMESIZE, (size_t)(p - name + 1)));
+	return buf;
+}
+
 void
 if_free(struct interface *ifp)
 {
@@ -295,6 +310,25 @@ if_valid_hwaddr(const uint8_t *hwaddr, size_t hwlen)
 	return false;
 }
 
+/* This utility function is used to work around case for lease file encoded in
+ * interface name after '='.  It assumes proper name in first arg and possibly
+ * "extended" name as a second one.  As a side-effect when the name matches and
+ * there is lease file encoded it is returned in the last optional argument. */
+int if_namecmp(const char *if_name, const char *ext_name, const char **lease)
+{
+	const char *p = strchr(ext_name, '=');
+	int ret;
+
+	if (p) {
+		ret = strncmp(if_name, ext_name, (size_t)(p - ext_name));
+		if (ret == 0 && lease)
+			*lease = p + 1;
+		return ret;
+	}
+
+	return strcmp(if_name, ext_name);
+}
+
 struct if_head *
 if_discover(struct dhcpcd_ctx *ctx, struct ifaddrs **ifaddrs,
     int argc, char * const *argv)
@@ -305,6 +339,9 @@ if_discover(struct dhcpcd_ctx *ctx, struct ifaddrs **ifaddrs,
 	struct if_head *ifs;
 	struct interface *ifp;
 	struct if_spec spec;
+	char ifn[IF_NAMESIZE];
+	const char *lease_id = NULL;
+
 #ifdef AF_LINK
 	const struct sockaddr_dl *sdl;
 #ifdef SIOCGIFPRIORITY
@@ -363,7 +400,8 @@ if_discover(struct dhcpcd_ctx *ctx, struct ifaddrs **ifaddrs,
 
 		if (argc > 0) {
 			for (i = 0; i < argc; i++) {
-				if (strcmp(argv[i], spec.devname) == 0)
+				if (if_namecmp(spec.devname, argv[i],
+					       &lease_id) == 0)
 					break;
 			}
 			active = (i == argc) ? IF_INACTIVE : IF_ACTIVE_USER;
@@ -371,7 +409,8 @@ if_discover(struct dhcpcd_ctx *ctx, struct ifaddrs **ifaddrs,
 			/* -1 means we're discovering against a specific
 			 * interface, but we still need the below rules
 			 * to apply. */
-			if (argc == -1 && strcmp(argv[0], spec.devname) != 0)
+			if (argc == -1 && if_namecmp(spec.devname, argv[0],
+						     &lease_id) != 0)
 				continue;
 			active = ctx->options & DHCPCD_INACTIVE ?
 			    IF_INACTIVE: IF_ACTIVE_USER;
@@ -383,7 +422,8 @@ if_discover(struct dhcpcd_ctx *ctx, struct ifaddrs **ifaddrs,
 		if (i < ctx->ifdc)
 			active = IF_INACTIVE;
 		for (i = 0; i < ctx->ifc; i++)
-			if (fnmatch(ctx->ifv[i], spec.devname, 0) == 0)
+			if (fnmatch(if_namepart(ifn, ctx->ifv[i]),
+				    spec.devname, 0) == 0)
 				break;
 		if (ctx->ifc && i == ctx->ifc)
 			active = IF_INACTIVE;
@@ -420,6 +460,9 @@ if_discover(struct dhcpcd_ctx *ctx, struct ifaddrs **ifaddrs,
 		}
 		ifp->ctx = ctx;
 		strlcpy(ifp->name, spec.devname, sizeof(ifp->name));
+		if (lease_id)
+			strlcpy(ifp->lease_identifier, lease_id,
+				LEASE_IDENTIFIER_LEN);
 		ifp->flags = ifa->ifa_flags;
 
 		if (ifa->ifa_addr != NULL) {
@@ -599,16 +642,21 @@ if_nametospec(const char *ifname, struct if_spec *spec)
 {
 	char *ep;
 	int e;
+	size_t len;
+
+	if (ifname == NULL || *ifname == '\0')
+		goto invalid;
+
+	ep = strchr(ifname, '=');
+	len = ep ? (size_t)(ep - ifname) : strlen(ifname);
+	len += 1; /* for ending NUL */
+
+	if (len > sizeof(spec->ifname) || len > sizeof(spec->drvname))
+		goto invalid;
+
+	strlcpy(spec->ifname, ifname, len);
+	strlcpy(spec->drvname, ifname, len);
 
-	if (ifname == NULL || *ifname == '\0' ||
-	    strlcpy(spec->ifname, ifname, sizeof(spec->ifname)) >=
-	    sizeof(spec->ifname) ||
-	    strlcpy(spec->drvname, ifname, sizeof(spec->drvname)) >=
-	    sizeof(spec->drvname))
-	{
-		errno = EINVAL;
-		return -1;
-	}
 	ep = strchr(spec->drvname, ':');
 	if (ep) {
 		spec->lun = (int)strtoi(ep + 1, NULL, 10, 0, INT_MAX, &e);
@@ -624,16 +672,18 @@ if_nametospec(const char *ifname, struct if_spec *spec)
 	strlcpy(spec->devname, spec->drvname, sizeof(spec->devname));
 	while (ep > spec->drvname && isdigit((int)*ep))
 		ep--;
-	if (*ep++ == ':') {
-		errno = EINVAL;
-		return -1;
-	}
+	if (*ep++ == ':')
+		goto invalid;
 	spec->ppa = (int)strtoi(ep, NULL, 10, 0, INT_MAX, &e);
 	if (e != 0)
 		spec->ppa = -1;
 	*ep = '\0';
 
 	return 0;
+
+invalid:
+	errno = EINVAL;
+	return -1;
 }
 
 static struct interface *
diff --git a/src/if.h b/src/if.h
index 91bba49b..fe5c4e23 100644
--- a/src/if.h
+++ b/src/if.h
@@ -111,6 +111,14 @@ int if_getifaddrs(struct ifaddrs **);
 #define	getifaddrs	if_getifaddrs
 #endif
 
+/* Basically this is strcmp but 2nd name can be suffixed with '=' and lease
+ * name after it - this suffix is skipped for comparison. */
+int if_namecmp(const char *if_name, const char *ext_name, const char **lease);
+/* This utility returns just an interface name from "extended" name.  If the
+ * name is not "extended" it is returned otherwise initial part is copied to buf
+ * and it is returned. */
+const char* if_namepart(char *buf, const char *ext_name);
+
 int if_getflags(struct interface *ifp);
 int if_setflag(struct interface *ifp, short flag);
 #define if_up(ifp) if_setflag((ifp), (IFF_UP | IFF_RUNNING))
-- 
2.33.0.800.g4c38ced690-goog