6 files changed, 63 insertions, 2 deletions

diff --git a/arp.c b/arp.c
index 44677ad..ad088b1 100644
--- a/arp.c
+++ b/arp.c
@@ -112,3 +112,37 @@ int arp(const struct ctx *c, struct iov_tail *data)
 
 	return 1;
 }
+
+/**
+ * arp_send_init_req() - Send initial ARP request to retrieve guest MAC address
+ * @c:		Execution context
+ */
+void arp_send_init_req(const struct ctx *c)
+{
+	struct {
+		struct ethhdr eh;
+		struct arphdr ah;
+		struct arpmsg am;
+	} __attribute__((__packed__)) req;
+
+	/* Ethernet header */
+	req.eh.h_proto = htons(ETH_P_ARP);
+	memcpy(req.eh.h_dest, MAC_BROADCAST, sizeof(req.eh.h_dest));
+	memcpy(req.eh.h_source, c->our_tap_mac, sizeof(req.eh.h_source));
+
+	/* ARP header */
+	req.ah.ar_op = htons(ARPOP_REQUEST);
+	req.ah.ar_hrd = htons(ARPHRD_ETHER);
+	req.ah.ar_pro = htons(ETH_P_IP);
+	req.ah.ar_hln = ETH_ALEN;
+	req.ah.ar_pln = 4;
+
+	/* ARP message */
+	memcpy(req.am.sha,	c->our_tap_mac,		sizeof(req.am.sha));
+	memcpy(req.am.sip,	&c->ip4.our_tap_addr,	sizeof(req.am.sip));
+	memcpy(req.am.tha,	MAC_BROADCAST,		sizeof(req.am.tha));
+	memcpy(req.am.tip,	&c->ip4.addr,		sizeof(req.am.tip));
+
+	debug("Sending initial ARP request for guest MAC address");
+	tap_send_single(c, &req, sizeof(req));
+}
diff --git a/arp.h b/arp.h
index 86bcbf8..d5ad0e1 100644
--- a/arp.h
+++ b/arp.h
@@ -21,5 +21,6 @@ struct arpmsg {
 } __attribute__((__packed__));
 
 int arp(const struct ctx *c, struct iov_tail *data);
+void arp_send_init_req(const struct ctx *c);
 
 #endif /* ARP_H */
diff --git a/ndp.c b/ndp.c
index eb090cd..588b48f 100644
--- a/ndp.c
+++ b/ndp.c
@@ -438,3 +438,23 @@ void ndp_timer(const struct ctx *c, const struct timespec *now)
 first:
 	next_ra = now->tv_sec + interval;
 }
+
+/**
+ * ndp_send_init_req() - Send initial NDP NS to retrieve guest MAC address
+ * @c:		Execution context
+ */
+void ndp_send_init_req(const struct ctx *c)
+{
+	struct ndp_ns ns = {
+		.ih = {
+			.icmp6_type		= NS,
+			.icmp6_code		= 0,
+			.icmp6_router		= 0, /* Reserved */
+			.icmp6_solicited	= 0, /* Reserved */
+			.icmp6_override		= 0, /* Reserved */
+		},
+		.target_addr = c->ip6.addr
+	};
+	debug("Sending initial NDP NS request for guest MAC address");
+	ndp_send(c, &c->ip6.addr, &ns, sizeof(ns));
+}
diff --git a/ndp.h b/ndp.h
index b1dd5e8..781ea86 100644
--- a/ndp.h
+++ b/ndp.h
@@ -11,5 +11,6 @@ struct icmp6hdr;
 int ndp(const struct ctx *c, const struct in6_addr *saddr,
 	struct iov_tail *data);
 void ndp_timer(const struct ctx *c, const struct timespec *now);
+void ndp_send_init_req(const struct ctx *c);
 
 #endif /* NDP_H */
diff --git a/passt.1 b/passt.1
index dd00b08..af5726a 100644
--- a/passt.1
+++ b/passt.1
@@ -330,8 +330,8 @@ selected IPv4 default route.
 
 .TP
 .BR \-\-no-ndp
-Disable NDP responses. NDP messages coming from guest or target namespace will
-be ignored.
+Disable Neighbor Discovery. NDP messages coming from guest or target
+namespace will be ignored. No initial NDP message will be sent.
 
 .TP
 .BR \-\-no-dhcpv6
diff --git a/tap.c b/tap.c
index 50e1a88..0f8ee25 100644
--- a/tap.c
+++ b/tap.c
@@ -1359,6 +1359,11 @@ static void tap_start_connection(const struct ctx *c)
 	ev.events = EPOLLIN | EPOLLRDHUP;
 	ev.data.u64 = ref.u64;
 	epoll_ctl(c->epollfd, EPOLL_CTL_ADD, c->fd_tap, &ev);
+
+	if (c->ifi4)
+		arp_send_init_req(c);
+	if (c->ifi6 && !c->no_ndp)
+		ndp_send_init_req(c);
 }
 
 /**