dhcpcd-discuss

Adds a command line option --noconfigure and checks at relevant
locations immediately before calling out into platform specific
code to configure a link.

This patch is incomplete in that it only covers the bits dealing
with IPv4.

Signed-off-by: Philipp Gesang <philipp.gesang@xxxxxxxxxxxxx>
---
 dhcp.c       |  2 +-
 if-linux.c   |  6 ++++++
 if-options.c |  9 ++++++++-
 if-options.h |  1 +
 ipv4.c       | 24 +++++++++++++++---------
 route.c      |  4 ++++
 6 files changed, 35 insertions(+), 11 deletions(-)

diff --git a/dhcp.c b/dhcp.c
index f2ee504..37c9886 100644
--- a/dhcp.c
+++ b/dhcp.c
@@ -760,7 +760,7 @@ make_message(struct bootp **bootpm, const struct interface *ifp, uint8_t type)
 	if ((mtu = if_getmtu(ifp)) == -1)
 		logger(ifp->ctx, LOG_ERR,
 		    "%s: if_getmtu: %m", ifp->name);
-	else if (mtu < MTU_MIN) {
+	else if (mtu < MTU_MIN && ifo->options & DHCPCD_CONFIGURE_LINK) {
 		if (if_setmtu(ifp, MTU_MIN) == -1)
 			logger(ifp->ctx, LOG_ERR,
 			    "%s: if_setmtu: %m", ifp->name);
diff --git a/if-linux.c b/if-linux.c
index 26f4d3c..1957c6a 100644
--- a/if-linux.c
+++ b/if-linux.c
@@ -226,6 +226,12 @@ if_init(struct interface *ifp)
 		return errno == ENOENT ? 0 : -1;
 	if (n == 1)
 		return 0;
+	if (!(ifp->ctx->options & DHCPCD_CONFIGURE_LINK)) {
+		logger(ifp->ctx, LOG_DEBUG,
+		       "%s: leaving IPv4 sysctl promote_secondaries unset",
+		       ifp->name);
+		return 0;
+	}
 	return write_path(path, "1") == -1 ? -1 : 0;
 }
 
diff --git a/if-options.c b/if-options.c
index 7dd6a43..02b69db 100644
--- a/if-options.c
+++ b/if-options.c
@@ -104,6 +104,7 @@
 #define O_LASTLEASE_EXTEND	O_BASE + 46
 #define O_INACTIVE		O_BASE + 47
 #define	O_MUDURL		O_BASE + 48
+#define	O_NOCONFIGURE		O_BASE + 49
 
 const struct option cf_options[] = {
 	{"background",      no_argument,       NULL, 'b'},
@@ -205,6 +206,7 @@ const struct option cf_options[] = {
 	{"lastleaseextend", no_argument,       NULL, O_LASTLEASE_EXTEND},
 	{"inactive",        no_argument,       NULL, O_INACTIVE},
 	{"mudurl",          required_argument, NULL, O_MUDURL},
+	{"noconfigure",     no_argument,       NULL, O_NOCONFIGURE},
 	{NULL,              0,                 NULL, '\0'}
 };
 
@@ -2146,6 +2148,10 @@ err_sla:
 		}
 		*ifo->mudurl = (uint8_t)s;
 		break;
+	case O_NOCONFIGURE:
+		logger(ctx, LOG_DEBUG, "all: suppressing link configuration");
+		ifo->options &= ~DHCPCD_CONFIGURE_LINK;
+		break;
 	default:
 		return 0;
 	}
@@ -2251,7 +2257,8 @@ default_config(struct dhcpcd_ctx *ctx)
 		logger(ctx, LOG_ERR, "%s: %m", __func__);
 		return NULL;
 	}
-	ifo->options |= DHCPCD_IF_UP | DHCPCD_LINK | DHCPCD_INITIAL_DELAY;
+	ifo->options |= DHCPCD_IF_UP | DHCPCD_LINK | DHCPCD_INITIAL_DELAY
+		| DHCPCD_CONFIGURE_LINK;
 	ifo->timeout = DEFAULT_TIMEOUT;
 	ifo->reboot = DEFAULT_REBOOT;
 	ifo->metric = -1;
diff --git a/if-options.h b/if-options.h
index 3f2eb04..93216f6 100644
--- a/if-options.h
+++ b/if-options.h
@@ -118,6 +118,7 @@
 #define DHCPCD_PRINT_PIDFILE		(1ULL << 59)
 #define DHCPCD_ONESHOT			(1ULL << 60)
 #define DHCPCD_INACTIVE			(1ULL << 61)
+#define DHCPCD_CONFIGURE_LINK		(1ULL << 62)
 
 #define DHCPCD_NODROP	(DHCPCD_EXITING | DHCPCD_PERSISTENT)
 
diff --git a/ipv4.c b/ipv4.c
index 57a19df..33efcea 100644
--- a/ipv4.c
+++ b/ipv4.c
@@ -513,6 +513,7 @@ delete_address(struct interface *ifp)
 	 * by a 3rd party. */
 	if (state->addr == NULL ||
 	    ifo->options & DHCPCD_INFORM ||
+	    !(ifo->options & DHCPCD_CONFIGURE_LINK) ||
 	    (ifo->options & DHCPCD_STATIC && ifo->req_addr.s_addr == 0))
 		return 0;
 	r = ipv4_deladdr(state->addr, 0);
@@ -638,15 +639,20 @@ ipv4_addaddr(struct interface *ifp, const struct in_addr *addr,
 		    ia->alias, ia->saddr);
 #endif
 
-	logger(ifp->ctx, LOG_DEBUG, "%s: adding IP address %s broadcast %s",
-	    ifp->name, ia->saddr, inet_ntoa(*bcast));
-	if (if_address(RTM_NEWADDR, ia) == -1) {
-		if (errno != EEXIST)
-			logger(ifp->ctx, LOG_ERR, "%s: if_addaddress: %m",
-			    __func__);
-		free(ia);
-		return NULL;
-	}
+	if (ifp->options->options & DHCPCD_CONFIGURE_LINK) {
+		logger(ifp->ctx, LOG_DEBUG, "%s: adding IP address %s broadcast %s",
+		       ifp->name, ia->saddr, inet_ntoa(*bcast));
+		if (if_address(RTM_NEWADDR, ia) == -1) {
+			if (errno != EEXIST)
+				logger(ifp->ctx, LOG_ERR, "%s: if_addaddress: %m",
+				       __func__);
+			free(ia);
+			return NULL;
+		}
+	} else
+		logger(ifp->ctx, LOG_DEBUG, "%s: skipping link config with lease "
+		       "data IP address %s broadcast %s",
+		       ifp->name, ia->saddr, inet_ntoa(*bcast));
 
 #ifdef ALIAS_ADDR
 	if (replaced) {
diff --git a/route.c b/route.c
index 1e6bd84..3da6cde 100644
--- a/route.c
+++ b/route.c
@@ -290,6 +290,8 @@ rt_add(struct rt *nrt, struct rt *ort)
 	    sa_is_unspecified(&nrt->rt_dest) &&
 	    sa_is_unspecified(&nrt->rt_netmask))
 		return false;
+	if (!(options & DHCPCD_CONFIGURE_LINK))
+		return false;
 
 	rt_desc(ort == NULL ? "adding" : "changing", nrt);
 
@@ -394,6 +396,8 @@ rt_delete(struct rt *rt)
 {
 	int retval;
 
+	if (!(rt->rt_ifp->options->options &  DHCPCD_CONFIGURE_LINK))
+		return false;
 	rt_desc("deleting", rt);
 	retval = if_route(RTM_DELETE, rt) == -1 ? false : true;
 	if (!retval && errno != ENOENT && errno != ESRCH)
-- 
2.4.11