I have a system with two network interfaces (em0 and em1), running dhcp
on both. Both dhcp servers provide me with a nameserver, but only one
of them works (I can't fix this). There is a config file for dhclient
I can use, but it only supports the supersede keyword. I don't want
to statically configure a nameserver override for em1, because the
whole point is that the good nameserver on em0 can change. I just
want to say "pretend this option did not arrive."
Diff below adds a little support for an ignore keyword. Like
supersede, except don't actually use the supplied value.
Index: clparse.c
===================================================================
RCS file: /cvs/src/sbin/dhclient/clparse.c,v
retrieving revision 1.38
diff -u -p -r1.38 clparse.c
--- clparse.c 10 Dec 2011 17:15:27 -0000 1.38
+++ clparse.c 27 Jul 2012 01:59:10 -0000
@@ -170,6 +170,11 @@ parse_client_statement(FILE *cfile)
if (code != -1)
config->default_actions[code] = ACTION_SUPERSEDE;
return;
+ case TOK_IGNORE:
+ code = parse_option_decl(cfile, &config->defaults[0]);
+ if (code != -1)
+ config->default_actions[code] = ACTION_IGNORE;
+ return;
case TOK_APPEND:
code = parse_option_decl(cfile, &config->defaults[0]);
if (code != -1)
Index: conflex.c
===================================================================
RCS file: /cvs/src/sbin/dhclient/conflex.c,v
retrieving revision 1.14
diff -u -p -r1.14 conflex.c
--- conflex.c 10 Dec 2011 17:36:40 -0000 1.14
+++ conflex.c 27 Jul 2012 01:15:19 -0000
@@ -337,6 +337,7 @@ static const struct keywords {
{ "filename", TOK_FILENAME },
{ "fixed-address", TOK_FIXED_ADDR },
{ "hardware", TOK_HARDWARE },
+ { "ignore", TOK_IGNORE },
{ "initial-interval", TOK_INITIAL_INTERVAL },
{ "interface", TOK_INTERFACE },
{ "lease", TOK_LEASE },
Index: dhclient.c
===================================================================
RCS file: /cvs/src/sbin/dhclient/dhclient.c,v
retrieving revision 1.146
diff -u -p -r1.146 dhclient.c
--- dhclient.c 9 Jul 2012 16:21:21 -0000 1.146
+++ dhclient.c 27 Jul 2012 01:59:35 -0000
@@ -1535,6 +1535,9 @@ priv_script_write_params(char *prefix, s
if (config->defaults[i].len) {
if (lease->options[i].len) {
switch (config->default_actions[i]) {
+ case ACTION_IGNORE:
+ /* handled below */
+ break;
case ACTION_DEFAULT:
dp = lease->options[i].data;
len = lease->options[i].len;
@@ -1588,6 +1591,9 @@ supersede:
len = lease->options[i].len;
dp = lease->options[i].data;
} else {
+ len = 0;
+ }
+ if (len && config->default_actions[i] == ACTION_IGNORE) {
len = 0;
}
if (len) {
Index: dhclient.conf.5
===================================================================
RCS file: /cvs/src/sbin/dhclient/dhclient.conf.5,v
retrieving revision 1.21
diff -u -p -r1.21 dhclient.conf.5
--- dhclient.conf.5 9 Apr 2011 19:53:00 -0000 1.21
+++ dhclient.conf.5 27 Jul 2012 02:05:28 -0000
@@ -244,6 +244,14 @@ in the
.Ic supersede
statement.
.It Xo
+.Ic ignore No { Op Ar option declaration
+.Oo , Ar ... option declaration Oc }
+.Xc
+If for some set of options the client should always ignore the
+value supplied by the server, these values can be defined in the
+.Ic ignore
+statement.
+.It Xo
.Ic prepend No { Op Ar option declaration
.Oo , Ar ... option declaration Oc }
.Xc
Index: dhcpd.h
===================================================================
RCS file: /cvs/src/sbin/dhclient/dhcpd.h,v
retrieving revision 1.76
diff -u -p -r1.76 dhcpd.h
--- dhcpd.h 9 Jul 2012 16:21:21 -0000 1.76
+++ dhcpd.h 27 Jul 2012 01:18:18 -0000
@@ -130,6 +130,7 @@ struct client_config {
struct option_data defaults[256];
enum {
ACTION_DEFAULT,
+ ACTION_IGNORE,
ACTION_SUPERSEDE,
ACTION_PREPEND,
ACTION_APPEND
Index: dhctoken.h
===================================================================
RCS file: /cvs/src/sbin/dhclient/dhctoken.h,v
retrieving revision 1.5
diff -u -p -r1.5 dhctoken.h
--- dhctoken.h 15 May 2006 08:10:57 -0000 1.5
+++ dhctoken.h 27 Jul 2012 01:15:54 -0000
@@ -79,6 +79,7 @@
#define TOK_REJECT 292
#define TOK_FDDI 293
#define TOK_LINK_TIMEOUT 294
+#define TOK_IGNORE 295
#define is_identifier(x) ((x) >= TOK_FIRST_TOKEN && \
(x) != TOK_STRING && \
