From a38901d5190608778ea9fb426e900ebdbf21cb67 Mon Sep 17 00:00:00 2001
From: Peter Qiu <zqiu@chromium.org>
Date: Wed, 9 Jun 2021 19:45:02 +0000
Subject: [PATCH 10/19] Add RPC support for DHCPv4 client

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.

Author: Paul Stewart <pstew@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/208835
Review URL: http://codereview.chromium.org/3061018
---
 src/Makefile        |  2 +-
 src/dhcp.c          | 20 ++++++++++---
 src/dhcpcd.c        |  7 +++++
 src/if-linux.c      | 11 ++++++++
 src/ipv4.c          | 12 ++++++--
 src/ipv4.h          |  2 +-
 src/rpc-interface.h | 51 +++++++++++++++++++++++++++++++++
 src/rpc-stub.c      | 69 +++++++++++++++++++++++++++++++++++++++++++++
 8 files changed, 166 insertions(+), 8 deletions(-)
 create mode 100644 src/rpc-interface.h
 create mode 100644 src/rpc-stub.c

diff --git a/src/Makefile b/src/Makefile
index fe78631d..c916bcc1 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -3,7 +3,7 @@
 PROG=		dhcpcd
 SRCS=		common.c control.c dhcpcd.c duid.c eloop.c logerr.c
 SRCS+=		if.c if-options.c sa.c route.c
-SRCS+=		dhcp-common.c script.c
+SRCS+=		dhcp-common.c script.c rpc-stub.c
 
 CFLAGS?=	-O2
 SUBDIRS+=	${MKDIRS}
diff --git a/src/dhcp.c b/src/dhcp.c
index 9cb64fbd..d0bb26e5 100644
--- a/src/dhcp.c
+++ b/src/dhcp.c
@@ -65,6 +65,7 @@
 #include "ipv4.h"
 #include "ipv4ll.h"
 #include "logerr.h"
+#include "rpc-interface.h"
 #include "sa.h"
 #include "script.h"
 
@@ -1965,6 +1966,7 @@ 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->nak_receive_count = 0;
 	state->failed_address_offer_count = 0;
@@ -1993,6 +1995,7 @@ 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);
@@ -2094,7 +2097,7 @@ dhcp_startrenew(void *arg)
 void
 dhcp_renew(struct interface *ifp)
 {
-
+	rpc_signal_status("Renew");
 	dhcp_startrenew(ifp);
 }
 
@@ -2105,6 +2108,7 @@ dhcp_rebind(void *arg)
 	struct dhcp_state *state = D_STATE(ifp);
 	struct dhcp_lease *lease = &state->lease;
 
+	rpc_signal_status("Rebind");
 	logwarnx("%s: failed to renew DHCP, rebinding", ifp->name);
 	logdebugx("%s: expire in %"PRIu32" seconds",
 	    ifp->name, lease->leasetime - lease->rebindtime);
@@ -2164,7 +2168,7 @@ 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);
@@ -2764,6 +2768,7 @@ dhcp_arp_address(struct interface *ifp)
 		    ifp->name, inet_ntoa(l.addr), inet_ntocidr(l.mask));
 		/* We need to handle DAD. */
 		arp_probe(astate);
+		rpc_signal_status("ArpSelf");
 		return 0;
 	}
 #endif
@@ -2823,6 +2828,7 @@ dhcp_inform(struct interface *ifp)
 	state = D_STATE(ifp);
 	ifo = ifp->options;
 
+	rpc_signal_status("Inform");
 	state->state = DHS_INFORM;
 	free(state->offer);
 	state->offer = NULL;
@@ -2982,6 +2988,7 @@ dhcp_reboot(struct interface *ifp)
 
 	if (state == NULL || state->state == DHS_NONE)
 		return;
+	rpc_signal_status("Reboot");
 	ifo = ifp->options;
 	state->state = DHS_REBOOT;
 	state->interval = 0;
@@ -3274,7 +3281,6 @@ dhcp_handledhcp(struct interface *ifp, struct bootp *bootp, size_t bootp_len,
 	struct if_options *ifo = ifp->options;
 	struct dhcp_lease *lease = &state->lease;
 	uint8_t type, tmp;
-	struct in_addr addr;
 	unsigned int i;
 	char *msg;
 	bool bootp_copied;
@@ -3445,7 +3451,8 @@ dhcp_handledhcp(struct interface *ifp, struct bootp *bootp, size_t bootp_len,
 		}
 		if (state->state == DHS_INFORM) /* INFORM should not be NAKed */
 			return;
-                LOGDHCP(logwarnx, "NAK (deferred)");
+		LOGDHCP(logwarnx, "NAK (deferred)");
+		rpc_signal_status("NakDefer");
 		if (state->nak_receive_count == 0)
 			eloop_timeout_add_sec(ifp->ctx->eloop, DHCP_BASE,
 					      handle_nak, ifp);
@@ -3517,6 +3524,7 @@ dhcp_handledhcp(struct interface *ifp, struct bootp *bootp, size_t bootp_len,
 	    &&
 	    (bootp->yiaddr == INADDR_ANY || bootp->yiaddr == INADDR_BROADCAST))
 	{
+		rpc_signal_status("IgnoreInvalidOffer");
 		LOGDHCP(logwarnx, "reject invalid address");
 		return;
 	}
@@ -3540,6 +3548,7 @@ dhcp_handledhcp(struct interface *ifp, struct bootp *bootp, size_t bootp_len,
 		if (bootp->yiaddr == state->failed.s_addr &&
 		    state->failed_address_offer_count == 0) {
 			LOGDHCP(logwarnx, "reject previously declined address");
+			rpc_signal_status("IgnoreFailedOffer");
 			state->failed_address_offer_count++;
 			return;
 		}
@@ -3605,12 +3614,14 @@ dhcp_handledhcp(struct interface *ifp, struct bootp *bootp, size_t bootp_len,
 	if (type) {
 		if (type == DHCP_OFFER) {
 			LOGDHCP(logwarnx, "ignoring offer of");
+			rpc_signal_status("IgnoreAdditionalOffer");
 			return;
 		}
 
 		/* We should only be dealing with acks */
 		if (type != DHCP_ACK) {
 			LOGDHCP(logerr, "not ACK or OFFER");
+			rpc_signal_status("IgnoreNonOffer");
 			return;
 		}
 
@@ -3658,6 +3669,7 @@ rapidcommit:
 
 #ifdef ARP
 	if ((ifo->options & DHCPCD_ARPGW) && (dhcp_probe_gw(ifp))) {
+		rpc_signal_status("ArpGateway");
 		return;
 	}
 
diff --git a/src/dhcpcd.c b/src/dhcpcd.c
index 7e778338..bba72a3d 100644
--- a/src/dhcpcd.c
+++ b/src/dhcpcd.c
@@ -65,6 +65,7 @@ const char dhcpcd_copyright[] = "Copyright (c) 2006-2019 Roy Marples";
 #include "ipv6.h"
 #include "ipv6nd.h"
 #include "logerr.h"
+#include "rpc-interface.h"
 #include "script.h"
 
 #ifdef HAVE_UTIL_H
@@ -1978,6 +1979,12 @@ printpidfile:
 	    (DHCPCD_MASTER | DHCPCD_DEV))
 		dev_start(&ctx);
 
+	if (rpc_init(&ctx) == -1) {
+		/* NB: rpc_init generates a syslog msg */
+		goto exit_failure;
+	}
+	rpc_signal_status("Init");
+
 	ctx.ifaces = if_discover(&ctx, &ifaddrs, ctx.ifc, ctx.ifv);
 	if (ctx.ifaces == NULL) {
 		logerr("%s: if_discover", __func__);
diff --git a/src/if-linux.c b/src/if-linux.c
index 3b7fa25c..f4437859 100644
--- a/src/if-linux.c
+++ b/src/if-linux.c
@@ -1198,6 +1198,10 @@ struct nlmr
 int
 if_route(unsigned char cmd, const struct rt *rt)
 {
+/* Do not modify route table when running in passive mode. */
+#ifdef PASSIVE_MODE
+	return 0;
+#endif
 	struct nlmr nlm;
 	bool gateway_unspec;
 
@@ -1457,6 +1461,10 @@ bpf_attach(int s, void *filter, unsigned int filter_len)
 int
 if_address(unsigned char cmd, const struct ipv4_addr *addr)
 {
+/* Do not modify addresses when running in passive mode. */
+#ifdef PASSIVE_MODE
+	return 0;
+#endif
 	struct nlma nlm;
 	int retval = 0;
 #if defined(IFA_F_NOPREFIXROUTE)
@@ -1511,6 +1519,9 @@ __unused const struct in_addr *addr, __unused const char *alias)
 int
 if_address6(unsigned char cmd, const struct ipv6_addr *ia)
 {
+#ifdef PASSIVE_MODE
+	return 0;
+#endif
 	struct nlma nlm;
 	struct ifa_cacheinfo cinfo;
 /* IFA_FLAGS is not a define, but is was added at the same time
diff --git a/src/ipv4.c b/src/ipv4.c
index 7a39c2c5..fd380750 100644
--- a/src/ipv4.c
+++ b/src/ipv4.c
@@ -55,6 +55,9 @@
 #include "route.h"
 #include "script.h"
 #include "sa.h"
+#ifdef PASSIVE_MODE
+#include "rpc-interface.h"
+#endif
 
 #define IPV4_LOOPBACK_ROUTE
 #if defined(__linux__) || defined(__sun) || (defined(BSD) && defined(RTF_LOCAL))
@@ -690,9 +693,8 @@ ipv4_daddaddr(struct interface *ifp, const struct dhcp_lease *lease)
 }
 
 void
-ipv4_applyaddr(void *arg)
+ipv4_applyaddr(struct interface *ifp)
 {
-	struct interface *ifp = arg;
 	struct dhcp_state *state = D_STATE(ifp);
 	struct dhcp_lease *lease;
 	struct if_options *ifo = ifp->options;
@@ -702,6 +704,12 @@ ipv4_applyaddr(void *arg)
 	if (state == NULL)
 		return;
 
+#ifdef PASSIVE_MODE
+	/* Note that in passive mode we still allow to update internal state
+	 * below - this is in order to have valid information (important in case
+	 * we need to e.g. renew) and to handle properly ARP. */
+	rpc_update_ipv4(ifp);
+#endif
 	lease = &state->lease;
 	if (state->new == NULL) {
 		if ((ifo->options & (DHCPCD_EXITING | DHCPCD_PERSISTENT)) !=
diff --git a/src/ipv4.h b/src/ipv4.h
index 506d83b5..5d15e01a 100644
--- a/src/ipv4.h
+++ b/src/ipv4.h
@@ -123,7 +123,7 @@ bool inet_getroutes(struct dhcpcd_ctx *, struct rt_head *);
 int ipv4_deladdr(struct ipv4_addr *, int);
 struct ipv4_addr *ipv4_addaddr(struct interface *,
     const struct in_addr *, const struct in_addr *, const struct in_addr *);
-void ipv4_applyaddr(void *);
+void ipv4_applyaddr(struct interface *);
 
 struct ipv4_addr *ipv4_iffindaddr(struct interface *,
     const struct in_addr *, const struct in_addr *);
diff --git a/src/rpc-interface.h b/src/rpc-interface.h
new file mode 100644
index 00000000..6e1e7e0c
--- /dev/null
+++ b/src/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/src/rpc-stub.c b/src/rpc-stub.c
new file mode 100644
index 00000000..aa650974
--- /dev/null
+++ b/src/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;
+}
+
-- 
2.33.0.800.g4c38ced690-goog