From: florian <florian@openbsd.org>
Date: Tue, 2 Mar 2021 12:03:50 +0000 (+0000)
Subject: Make unveiling the lease directory a warning instead of a fatal error
X-Git-Url: http://artulab.com/gitweb/?a=commitdiff_plain;h=ae968ffd159a87bf1d6a452172c6c5cf1b154f48;p=openbsd

Make unveiling the lease directory a warning instead of a fatal error
when the lease directory does not exist.
This means that dhcpleased(8) will no longer request a previously
configured IP address from the dhcp server and will fall back to
DHCPDISCOVER which requests any IP address from the dhcp server.

This likely makes diskless(8) work with dhcpleased(8).

A normal diskless(8) setup has only / mounted via nfs when
dhcpleased(8) starts. /var exists but nothing is mounted there yet,
meaning /var/db/dhcpleased does not exist so lease files are disabled.
dhcpleased(8) sends a DHCPDISCOVER to request any IP address but since
the dhcp server has (very likely) a 'fixed-address' configured we get
the same IP back that is already configured.

If /var/db/dhcpleased/ exists on / (and /var is *NOT* mounted later)
in a diskless(8) setup, care must be taken that the root file system is
not shared between machines.

If /var/db/dhcpleased/ exists on / and /var on NFS is mounted over
this later bad things probably happen. This is a configuration error
and must befixed.

discussed with deraadt@

Actuall tests on existing diskless(8) setups would be appreciated.
---

diff --git a/sbin/dhcpleased/dhcpleased.c b/sbin/dhcpleased/dhcpleased.c
index 27b70e1af0e..d2c936aab03 100644
--- a/sbin/dhcpleased/dhcpleased.c
+++ b/sbin/dhcpleased/dhcpleased.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: dhcpleased.c,v 1.5 2021/03/02 12:01:39 florian Exp $	*/
+/*	$OpenBSD: dhcpleased.c,v 1.6 2021/03/02 12:03:50 florian Exp $	*/
 
 /*
  * Copyright (c) 2017, 2021 Florian Obser <florian@openbsd.org>
@@ -90,7 +90,7 @@ static struct imsgev	*iev_engine;
 pid_t			 frontend_pid;
 pid_t			 engine_pid;
 
-int			 routesock, ioctl_sock, rtm_seq = 0;
+int			 routesock, ioctl_sock, rtm_seq, no_lease_files;
 
 void
 main_sig_handler(int sig, short event, void *arg)
@@ -267,8 +267,10 @@ main(int argc, char *argv[])
 	if (unveil("/dev/bpf", "rw") == -1)
 		fatal("unveil /dev/bpf");
 
-	if (unveil(_PATH_LEASE, "rwc") == -1)
-		fatal("unveil " _PATH_LEASE);
+	if (unveil(_PATH_LEASE, "rwc") == -1) {
+		no_lease_files = 1;
+		log_warn("disabling lease files, unveil " _PATH_LEASE);
+	}
 
 	if (unveil(NULL, NULL) == -1)
 		fatal("locking unveil");
@@ -714,6 +716,9 @@ configure_interface(struct imsg_configure_interface *imsg)
 	main_imsg_compose_frontend(IMSG_UDPSOCK, udpsock,
 	    &imsg->if_index, sizeof(imsg->if_index));
 
+	if (no_lease_files)
+		return;
+
 	if (inet_ntop(AF_INET, &imsg->addr, ntop_buf, sizeof(ntop_buf)) ==
 	    NULL) {
 		log_warn("%s: inet_ntop", __func__);
@@ -965,6 +970,9 @@ read_lease_file(struct imsg_ifinfo *imsg_ifinfo)
 	char	 if_name[IF_NAMESIZE];
 	char	 lease_file_buf[sizeof(_PATH_LEASE) + IF_NAMESIZE];
 
+	if (no_lease_files)
+		return;
+
 	memset(imsg_ifinfo->lease, 0, sizeof(imsg_ifinfo->lease));
 
 	if (if_indextoname(imsg_ifinfo->if_index, if_name) == 0) {