[PATCH] Add RPC support for DHCPv4 client

Cherry-picked from
https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/
master/net-misc/dhcpcd/files/patches/dhcpcd-6.8.2-Add-RPC-support-for-
DHCPv4-client.patch.

Define a RPC interface for the daemon to interact with other
applications (command execution and status update), and integrate
it with the DHCPv4 client.  Default to stub implementation for now
until new RPC mechanism is implemented and enabled.

Also add a new compiler flag "PASSIVE_MODE" which will be enabled
when a RPC mechanism is enabled (e.g. DBus).  This compiler flag
will prevent the daemon from modifying system configurations
(e.g. routing table, interface address).  The idea is that when
RPC is enabled, the daemon will provide configurations through
RPC, and the remote application will be the one responsible for
modifying system configurations.

Integration with DHCPv6 client will be added in the future.

BUG: 22956197
Change-Id: I7147d13e2cfab5c209c1ab862f33ef9d1b1dddaf

Reviewed-on: https://chromium-review.googlesource.com/208835
Review URL: http://codereview.chromium.org/3061018

6 files changed, 159 insertions, 3 deletions

diff --git a/Makefile b/Makefile
index 36ff297..f277750 100644
--- a/Makefile
+++ b/Makefile
@@ -2,7 +2,7 @@
 
 PROG=		dhcpcd
 SRCS=		common.c control.c dhcpcd.c duid.c eloop.c
-SRCS+=		if.c if-options.c script.c
+SRCS+=		if.c if-options.c script.c rpc-stub.c
 SRCS+=		dhcp-common.c
 
 CFLAGS?=	-O2
diff --git a/dhcp.c b/dhcp.c
index 474e6c0..dd9be05 100644
--- a/dhcp.c
+++ b/dhcp.c
@@ -61,6 +61,7 @@
 #include "if.h"
 #include "ipv4.h"
 #include "ipv4ll.h"
+#include "rpc-interface.h"
 #include "script.h"
 
 #define DAD		"Duplicate address detected"
@@ -1820,6 +1821,7 @@ dhcp_discover(void *arg)
 	struct dhcp_state *state = D_STATE(ifp);
 	struct if_options *ifo = ifp->options;
 
+	rpc_signal_status("Discover");
 	state->state = DHS_DISCOVER;
 	state->xid = dhcp_xid(ifp);
 	state->nak_receive_count = 0;
@@ -1849,6 +1851,7 @@ dhcp_request(void *arg)
 	struct interface *ifp = arg;
 	struct dhcp_state *state = D_STATE(ifp);
 
+	rpc_signal_status("Request");
 	state->state = DHS_REQUEST;
 	state->nak_receive_count = 0;
 	send_request(ifp);
@@ -1882,6 +1885,7 @@ dhcp_renew(void *arg)
 	struct dhcp_state *state = D_STATE(ifp);
 	struct dhcp_lease *lease = &state->lease;
 
+	rpc_signal_status("Renew");
 	logger(ifp->ctx, LOG_DEBUG, "%s: renewing lease of %s",
 	    ifp->name, inet_ntoa(lease->addr));
 	logger(ifp->ctx, LOG_DEBUG, "%s: rebind in %"PRIu32" seconds,"
@@ -1910,6 +1914,7 @@ dhcp_rebind(void *arg)
 	struct dhcp_state *state = D_STATE(ifp);
 	struct dhcp_lease *lease = &state->lease;
 
+	rpc_signal_status("Rebind");
 	logger(ifp->ctx, LOG_WARNING,
 	    "%s: failed to renew DHCP, rebinding", ifp->name);
 	logger(ifp->ctx, LOG_DEBUG, "%s: expire in %"PRIu32" seconds",
@@ -2308,6 +2313,7 @@ dhcp_inform(struct interface *ifp)
 		}
 	}
 
+	rpc_signal_status("Inform");
 	state->state = DHS_INFORM;
 	state->xid = dhcp_xid(ifp);
 	send_inform(ifp);
@@ -2341,6 +2347,7 @@ dhcp_reboot(struct interface *ifp)
 
 	if (state == NULL)
 		return;
+	rpc_signal_status("Reboot");
 	ifo = ifp->options;
 	state->state = DHS_REBOOT;
 	state->interval = 0;
@@ -2595,7 +2602,7 @@ dhcp_probe_gw_response(struct arp_state *astate, const struct arp_msg *amsg)
 	    amsg->sip.s_addr == astate->addr.s_addr) {
 		if (astate->dest_hwlen) {
 			/* Response to unicast ARP. */
-			/* TODO(zqiu): notify listener. */
+			rpc_notify_unicast_arp(astate->iface);
 		} else {
 			/* Response to arpgw request. */
 			save_gateway_addr(astate->iface, amsg->sha);
@@ -2933,6 +2940,7 @@ dhcp_handledhcp(struct interface *ifp, struct dhcp_message **dhcpp,
 			return;
 
 		log_dhcp(LOG_WARNING, "NAK (deferred):", ifp, dhcp, from);
+		rpc_signal_status("NakDefer");
 		if (state->nak_receive_count == 0)
 			eloop_timeout_add_sec(ifp->ctx->eloop,
 					      DHCP_BASE, handle_nak, ifp);
@@ -3008,6 +3016,7 @@ dhcp_handledhcp(struct interface *ifp, struct dhcp_message **dhcpp,
 	    (dhcp->ciaddr == INADDR_ANY || dhcp->ciaddr == INADDR_BROADCAST) &&
 	    (dhcp->yiaddr == INADDR_ANY || dhcp->yiaddr == INADDR_BROADCAST))
 	{
+		rpc_signal_status("IgnoreInvalidOffer");
 		log_dhcp(LOG_WARNING, "reject invalid address",
 		    ifp, dhcp, from);
 		return;
@@ -3036,6 +3045,7 @@ dhcp_handledhcp(struct interface *ifp, struct dhcp_message **dhcpp,
 			log_dhcp(LOG_WARNING,
 				 "reject previously declined address",
 				 ifp, dhcp, from);
+			rpc_signal_status("IgnoreFailedOffer");
 			state->failed_address_offer_count++;
 			return;
 		}
@@ -3079,6 +3089,7 @@ dhcp_handledhcp(struct interface *ifp, struct dhcp_message **dhcpp,
 		if (type == DHCP_OFFER) {
 			log_dhcp(LOG_WARNING, "ignoring offer of",
 			    ifp, dhcp, from);
+			rpc_signal_status("IgnoreAdditionalOffer");
 			return;
 		}
 
@@ -3086,6 +3097,7 @@ dhcp_handledhcp(struct interface *ifp, struct dhcp_message **dhcpp,
 		if (type != DHCP_ACK) {
 			log_dhcp(LOG_ERR, "not ACK or OFFER",
 			    ifp, dhcp, from);
+			rpc_signal_status("IgnoreNonOffer");
 			return;
 		}
 
@@ -3133,6 +3145,7 @@ dhcp_handledhcp(struct interface *ifp, struct dhcp_message **dhcpp,
 #ifndef IN_IFF_TENTATIVE
 				arp_probe(astate);
 #endif
+				rpc_signal_status("ArpSelf");
 			}
 #ifndef IN_IFF_TENTATIVE
 			return;
@@ -3141,6 +3154,7 @@ dhcp_handledhcp(struct interface *ifp, struct dhcp_message **dhcpp,
 	}
 
 	if ((ifo->options & DHCPCD_ARPGW) && (dhcp_probe_gw(ifp))) {
+		rpc_signal_status("ArpGateway");
 		return;
 	}
 
diff --git a/dhcpcd.c b/dhcpcd.c
index 763e06f..a486ac2 100644
--- a/dhcpcd.c
+++ b/dhcpcd.c
@@ -63,6 +63,7 @@ const char dhcpcd_copyright[] = "Copyright (c) 2006-2015 Roy Marples";
 #include "ipv4.h"
 #include "ipv6.h"
 #include "ipv6nd.h"
+#include "rpc-interface.h"
 #include "script.h"
 
 #ifdef USE_SIGNALS
@@ -1777,6 +1778,12 @@ main(int argc, char **argv)
 	    (DHCPCD_MASTER | DHCPCD_DEV))
 		dev_start(&ctx);
 
+	if (rpc_init(&ctx) == -1) {
+		/* NB: rpc_init generates a syslog msg */
+		exit(EXIT_FAILURE);
+	}
+	rpc_signal_status("Init");
+
 	ctx.ifaces = if_discover(&ctx, ctx.ifc, ctx.ifv);
 	if (ctx.ifaces == NULL) {
 		logger(&ctx, LOG_ERR, "if_discover: %m");
diff --git a/ipv4.c b/ipv4.c
index d088d80..f7b0d22 100644
--- a/ipv4.c
+++ b/ipv4.c
@@ -47,6 +47,9 @@
 #include "if-options.h"
 #include "ipv4.h"
 #include "script.h"
+#ifdef PASSIVE_MODE
+#include "rpc-interface.h"
+#endif
 
 #define IPV4_LOOPBACK_ROUTE
 #if defined(__linux__) || (defined(BSD) && defined(RTF_LOCAL))
@@ -642,6 +645,8 @@ add_router_host_route(struct rt_head *rt, const struct interface *ifp)
 void
 ipv4_buildroutes(struct dhcpcd_ctx *ctx)
 {
+/* Do not modify route table when running in passive mode. */
+#ifndef PASSIVE_MODE
 	struct rt_head *nrs, *dnr;
 	struct rt *or, *rt, *rtn;
 	struct interface *ifp;
@@ -731,14 +736,16 @@ ipv4_buildroutes(struct dhcpcd_ctx *ctx)
 	}
 	ipv4_freeroutes(ctx->ipv4_routes);
 	ctx->ipv4_routes = nrs;
+#endif
 }
 
 int
 ipv4_deladdr(struct interface *ifp,
     const struct in_addr *addr, const struct in_addr *net)
 {
+	int r = 0;
+#ifndef PASSIVE_MODE
 	struct dhcp_state *dstate;
-	int r;
 	struct ipv4_state *state;
 	struct ipv4_addr *ap;
 
@@ -769,6 +776,7 @@ ipv4_deladdr(struct interface *ifp,
 			break;
 		}
 	}
+#endif
 	return r;
 }
 
@@ -870,6 +878,7 @@ ipv4_finalisert(struct interface *ifp)
 void
 ipv4_finaliseaddr(struct interface *ifp)
 {
+#ifndef PASSIVE_MODE
 	struct dhcp_state *state = D_STATE(ifp);
 	struct dhcp_lease *lease;
 
@@ -886,11 +895,15 @@ ipv4_finaliseaddr(struct interface *ifp)
 	state->addr.s_addr = lease->addr.s_addr;
 	state->net.s_addr = lease->net.s_addr;
 	ipv4_finalisert(ifp);
+#endif
 }
 
 void
 ipv4_applyaddr(void *arg)
 {
+#ifdef PASSIVE_MODE
+	rpc_update_ipv4(arg);
+#else
 	struct interface *ifp = arg, *ifn;
 	struct dhcp_state *state = D_STATE(ifp), *nstate;
 	struct dhcp_message *dhcp;
@@ -1008,6 +1021,8 @@ ipv4_applyaddr(void *arg)
 #endif
 
 	ipv4_finaliseaddr(ifp);
+
+#endif  /* PASSIVE_MODE */
 }
 
 void
diff --git a/rpc-interface.h b/rpc-interface.h
new file mode 100644
index 0000000..6e1e7e0
--- /dev/null
+++ b/rpc-interface.h
@@ -0,0 +1,51 @@
+/*
+ * dhcpcd - DHCP client daemon
+ * Copyright (c) 2006-2015 Roy Marples <roy@marples.name>
+ * All rights reserved
+
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#ifndef RPC_INTERFACE_H
+#define RPC_INTERFACE_H
+
+#include "dhcpcd.h"
+
+/* Initialize RPC interface. Return 0 on success. */
+int rpc_init(struct dhcpcd_ctx *ctx);
+
+/* Tear down RPC interface. */
+void rpc_close(void);
+
+/* Emit signal status to RPC interface. */
+void rpc_signal_status(const char *);
+
+/* Update IPv4 configuration. Return 0 on success. */
+int rpc_update_ipv4(struct interface *ifp);
+
+/* Update IPv6 configuration. Return 0 on success. */
+int rpc_update_ipv6(struct interface *ifp);
+
+/* Emit notification for successful unicast ARP. Return 0 on success. */
+int rpc_notify_unicast_arp(struct interface *ifp);
+
+#endif
diff --git a/rpc-stub.c b/rpc-stub.c
new file mode 100644
index 0000000..aa65097
--- /dev/null
+++ b/rpc-stub.c
@@ -0,0 +1,69 @@
+/*
+ * dhcpcd - DHCP client daemon
+ * Copyright (c) 2006-2015 Roy Marples <roy@marples.name>
+ * All rights reserved
+
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include "rpc-interface.h"
+
+int
+rpc_init(struct dhcpcd_ctx *ctx)
+{
+	/* Stub implementation. */
+	return 0;
+}
+
+void
+rpc_close(void)
+{
+	/* Stub implementation. */
+}
+
+void
+rpc_signal_status(const char *reason)
+{
+	/* Stub implementation. */
+}
+
+int
+rpc_update_ipv4(struct interface *ifp)
+{
+	/* Stub implementation. */
+	return 0;
+}
+
+int
+rpc_update_ipv6(struct interface *ifp)
+{
+	/* Stub implementation. */
+	return 0;
+}
+
+int
+rpc_notify_unicast_arp(struct interface *ifp)
+{
+	/* Stub implementation. */
+	return 0;
+}
+