[Dnsmasq-discuss] [PATCH] Support for reading the ISC dhcp lease file
Michael Tremer
michael.tremer at ipfire.org
Wed Jul 30 11:51:26 BST 2014
Hello fellow dnsmasq users,
I am working on the free firewall distribution called IPFire
(www.ipfire.org) and inside of that distribution, dnsmasq is used as a
DNS proxy. For the DHCP services, we use the ISC dhcp daemon.
In the past, dnsmasq supported importing the leases from the ISC dhcpd
lease file which then was unfortunately removed because the code was
unmaintainable. I am not fully aware of the reasons.
Our workaround was to stick with a very old version of dnsmasq. Now that
there are things like DNSSEC and that backporting security fixes it not
a pleasant thing to do, I took the old code and made it work with the
current master branch.
I started with the old code from John Volpe and Simon and cleaned it up
step by step. Some things like parsing the date was unnecessarily
complicated and I think that the attached patch is much cleaner. It has
been tested a lot by our community and is working well.
There is also a git branch where you can pull my changes from:
http://git.ipfire.org/?p=people/ms/dnsmasq.git;a=shortlog;h=refs/heads/dhcp-lease
I would really like to see this included in dnsmasq. There are also
various bugs in the bugtrackers of various distributions like Debian and
so on.
Maybe we can work out the problems and get this merged.
Best,
-Michael
diff --git a/Makefile b/Makefile
index 292c8bd..5e0cdbe 100644
--- a/Makefile
+++ b/Makefile
@@ -69,7 +69,7 @@ objs = cache.o rfc1035.o util.o option.o forward.o network.o \
dnsmasq.o dhcp.o lease.o rfc2131.o netlink.o dbus.o bpf.o \
helper.o tftp.o log.o conntrack.o dhcp6.o rfc3315.o \
dhcp-common.o outpacket.o radv.o slaac.o auth.o ipset.o \
- domain.o dnssec.o blockdata.o
+ domain.o dnssec.o blockdata.o isc.o
hdrs = dnsmasq.h config.h dhcp-protocol.h dhcp6-protocol.h \
dns-protocol.h radv-protocol.h ip6addr.h
diff --git a/src/cache.c b/src/cache.c
index 5cec918..1f5657f 100644
--- a/src/cache.c
+++ b/src/cache.c
@@ -17,7 +17,7 @@
#include "dnsmasq.h"
static struct crec *cache_head = NULL, *cache_tail = NULL, **hash_table = NULL;
-#ifdef HAVE_DHCP
+#if (defined HAVE_DHCP) || (defined HAVE_ISC_READER)
static struct crec *dhcp_spare = NULL;
#endif
static struct crec *new_chain = NULL;
@@ -222,6 +222,9 @@ static void cache_free(struct crec *crecp)
crecp->flags &= ~F_BIGNAME;
}
+ if (crecp->flags & F_DHCP)
+ free(crecp->name.namep);
+
#ifdef HAVE_DNSSEC
cache_blockdata_free(crecp);
#endif
@@ -1110,7 +1113,7 @@ void cache_reload(void)
total_size = read_hostsfile(ah->fname, ah->index, total_size, (struct crec **)daemon->packet, revhashsz);
}
-#ifdef HAVE_DHCP
+#if (defined HAVE_DHCP) || (defined HAVE_ISC_READER)
struct in_addr a_record_from_hosts(char *name, time_t now)
{
struct crec *crecp = NULL;
@@ -1188,7 +1191,7 @@ void cache_add_dhcp_entry(char *host_name, int prot,
addrlen = sizeof(struct in6_addr);
}
#endif
-
+
inet_ntop(prot, host_address, daemon->addrbuff, ADDRSTRLEN);
while ((crec = cache_find_by_name(crec, host_name, 0, flags | F_CNAME)))
@@ -1253,7 +1256,11 @@ void cache_add_dhcp_entry(char *host_name, int prot,
else
crec->ttd = ttd;
crec->addr.addr = *host_address;
+#ifdef HAVE_ISC_READER
+ crec->name.namep = strdup(host_name);
+#else
crec->name.namep = host_name;
+#endif
crec->uid = next_uid();
cache_hash(crec);
diff --git a/src/dnsmasq.c b/src/dnsmasq.c
index 1c96a0e..156ac9a 100644
--- a/src/dnsmasq.c
+++ b/src/dnsmasq.c
@@ -934,6 +934,11 @@ int main (int argc, char **argv)
poll_resolv(0, daemon->last_resolv != 0, now);
daemon->last_resolv = now;
+
+#ifdef HAVE_ISC_READER
+ if (daemon->lease_file && !daemon->dhcp)
+ load_dhcp(now);
+#endif
}
if (FD_ISSET(piperead, &rset))
diff --git a/src/dnsmasq.h b/src/dnsmasq.h
index 3032546..a40b2a9 100644
--- a/src/dnsmasq.h
+++ b/src/dnsmasq.h
@@ -1447,3 +1447,8 @@ void slaac_add_addrs(struct dhcp_lease *lease, time_t now, int force);
time_t periodic_slaac(time_t now, struct dhcp_lease *leases);
void slaac_ping_reply(struct in6_addr *sender, unsigned char *packet, char *interface, struct dhcp_lease *leases);
#endif
+
+/* isc.c */
+#ifdef HAVE_ISC_READER
+void load_dhcp(time_t now);
+#endif
diff --git a/src/isc.c b/src/isc.c
new file mode 100644
index 0000000..5106442
--- /dev/null
+++ b/src/isc.c
@@ -0,0 +1,251 @@
+/* dnsmasq is Copyright (c) 2014 John Volpe, Simon Kelley and
+ Michael Tremer
+
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; version 2 dated June, 1991, or
+ (at your option) version 3 dated 29 June, 2007.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+ Code in this file is based on contributions by John Volpe and
+ Simon Kelley. Updated for recent versions of dnsmasq by
+ Michael Tremer.
+*/
+
+#include "dnsmasq.h"
+
+#ifdef HAVE_ISC_READER
+#define MAXTOK 50
+
+struct isc_dhcp_lease {
+ char* name;
+ char* fqdn;
+ time_t expires;
+ struct in_addr addr;
+ struct isc_dhcp_lease* next;
+};
+
+static struct isc_dhcp_lease* dhcp_lease_new(const char* hostname) {
+ struct isc_dhcp_lease* lease = whine_malloc(sizeof(*lease));
+
+ lease->name = strdup(hostname);
+ if (daemon->domain_suffix) {
+ asprintf(&lease->fqdn, "%s.%s", hostname, daemon->domain_suffix);
+ }
+ lease->expires = 0;
+ lease->next = NULL;
+
+ return lease;
+}
+
+static void dhcp_lease_free(struct isc_dhcp_lease* lease) {
+ if (!lease)
+ return;
+
+ if (lease->name)
+ free(lease->name);
+ if (lease->fqdn)
+ free(lease->fqdn);
+ free(lease);
+}
+
+static int next_token(char* token, int buffsize, FILE* fp) {
+ int c, count = 0;
+ char* cp = token;
+
+ while ((c = getc(fp)) != EOF) {
+ if (c == '#') {
+ do {
+ c = getc(fp);
+ } while (c != '\n' && c != EOF);
+ }
+
+ if (c == ' ' || c == '\t' || c == '\n' || c == ';') {
+ if (count)
+ break;
+ } else if ((c != '"') && (count < buffsize - 1)) {
+ *cp++ = c;
+ count++;
+ }
+ }
+
+ *cp = 0;
+ return count ? 1 : 0;
+}
+
+static long get_utc_offset() {
+ time_t t = time(NULL);
+ struct tm* time_struct = localtime(&t);
+
+ return time_struct->tm_gmtoff;
+}
+
+static time_t parse_lease_time(const char* token_date, const char* token_time) {
+ time_t time = (time_t)(-1);
+ struct tm lease_time;
+
+ if (sscanf(token_date, "%d/%d/%d", &lease_time.tm_year, &lease_time.tm_mon, &lease_time.tm_mday) == 3) {
+ lease_time.tm_year -= 1900;
+ lease_time.tm_mon -= 1;
+
+ if (sscanf(token_time, "%d:%d:%d", &lease_time.tm_hour, &lease_time.tm_min, &lease_time.tm_sec) == 3) {
+ time = mktime(&lease_time) + get_utc_offset();
+ }
+ }
+
+ return time;
+}
+
+static struct isc_dhcp_lease* find_lease(const char* hostname, struct isc_dhcp_lease* leases) {
+ struct isc_dhcp_lease* lease = leases;
+
+ while (lease) {
+ if (strcmp(hostname, lease->name) == 0) {
+ return lease;
+ }
+ lease = lease->next;
+ }
+
+ return NULL;
+}
+
+static off_t lease_file_size = (off_t)0;
+static ino_t lease_file_inode = (ino_t)0;
+
+void load_dhcp(time_t now) {
+ struct isc_dhcp_lease* leases = NULL;
+
+ struct stat statbuf;
+ if (stat(daemon->lease_file, &statbuf) == -1) {
+ return;
+ }
+
+ /* Do nothing if the lease file has not changed. */
+ if ((statbuf.st_size <= lease_file_size) && (statbuf.st_ino == lease_file_inode))
+ return;
+
+ lease_file_size = statbuf.st_size;
+ lease_file_inode = statbuf.st_ino;
+
+ FILE* fp = fopen(daemon->lease_file, "r");
+ if (!fp) {
+ my_syslog(LOG_ERR, _("failed to load %s:%s"), daemon->lease_file, strerror(errno));
+ return;
+ }
+
+ my_syslog(LOG_INFO, _("reading %s"), daemon->lease_file);
+
+ char* hostname = daemon->namebuff;
+ struct in_addr host_address;
+ time_t time_starts = -1;
+ time_t time_ends = -1;
+ int nomem;
+
+ char token[MAXTOK];
+ while ((next_token(token, MAXTOK, fp))) {
+ if (strcmp(token, "lease") == 0) {
+ hostname[0] = '\0';
+
+ if (next_token(token, MAXTOK, fp) && ((host_address.s_addr = inet_addr(token)) != (in_addr_t)-1)) {
+ if (next_token(token, MAXTOK, fp) && *token == '{') {
+ while (next_token(token, MAXTOK, fp) && *token != '}') {
+ if ((strcmp(token, "client-hostname") == 0) || (strcmp(token, "hostname") == 0)) {
+ if (next_token(hostname, MAXDNAME, fp)) {
+ if (!canonicalise(hostname, &nomem)) {
+ *hostname = 0;
+ my_syslog(LOG_ERR, _("bad name in %s"), daemon->lease_file);
+ }
+ }
+ } else if ((strcmp(token, "starts") == 0) || (strcmp(token, "ends") == 0)) {
+ char token_date[MAXTOK];
+ char token_time[MAXTOK];
+
+ int is_starts = strcmp(token, "starts") == 0;
+
+ // Throw away the weekday and parse the date.
+ if (next_token(token, MAXTOK, fp) && next_token(token_date, MAXTOK, fp) && next_token(token_time, MAXTOK, fp)) {
+ time_t time = parse_lease_time(token_date, token_time);
+
+ if (is_starts)
+ time_starts = time;
+ else
+ time_ends = time;
+ }
+ }
+ }
+
+ if (!*hostname)
+ continue;
+
+ if ((time_starts == -1) || (time_ends == -1))
+ continue;
+
+ if (difftime(now, time_ends) > 0)
+ continue;
+
+ char* dot = strchr(hostname, '.');
+ if (dot) {
+ if (!daemon->domain_suffix || hostname_isequal(dot + 1, daemon->domain_suffix)) {
+ my_syslog(LOG_WARNING,
+ _("Ignoring DHCP lease for %s because it has an illegal domain part"),
+ hostname);
+ continue;
+ }
+ *dot = 0;
+ }
+
+ // Search for an existing lease in the list
+ // with the given host name and update the data
+ // if needed.
+ struct isc_dhcp_lease* lease = find_lease(hostname, leases);
+
+ // If no lease already exists, we create a new one
+ // and append it to the list.
+ if (!lease) {
+ lease = dhcp_lease_new(hostname);
+
+ lease->next = leases;
+ leases = lease;
+ }
+
+ // Only update more recent leases.
+ if (lease->expires > time_ends)
+ continue;
+
+ lease->addr = host_address;
+ lease->expires = time_ends;
+ }
+ }
+ }
+ }
+
+ fclose(fp);
+
+ // Drop all entries.
+ cache_unhash_dhcp();
+
+ while (leases) {
+ struct isc_dhcp_lease *lease = leases;
+ leases = lease->next;
+
+ if (lease->fqdn) {
+ cache_add_dhcp_entry(lease->fqdn, AF_INET, (struct all_addr*)&lease->addr.s_addr, lease->expires);
+ }
+
+ if (lease->name) {
+ cache_add_dhcp_entry(lease->name, AF_INET, (struct all_addr*)&lease->addr.s_addr, lease->expires);
+ }
+
+ // Cleanup
+ dhcp_lease_free(lease);
+ }
+}
+
+#endif
diff --git a/src/option.c b/src/option.c
index daa728f..d16c982 100644
--- a/src/option.c
+++ b/src/option.c
@@ -1642,7 +1642,7 @@ static int one_opt(int option, char *arg, char *errstr, char *gen_err, int comma
ret_err(_("bad MX target"));
break;
-#ifdef HAVE_DHCP
+#if (defined HAVE_DHCP) || (defined HAVE_ISC_READER)
case 'l': /* --dhcp-leasefile */
daemon->lease_file = opt_string_alloc(arg);
break;
More information about the Dnsmasq-discuss
mailing list