From ebf2794ba9df8c3e968f55bb357526c480374868 Mon Sep 17 00:00:00 2001
From: Ben Pfaff <blp@nicira.com>
Date: Wed, 16 Jul 2008 17:01:03 -0700
Subject: [PATCH] Answer ARP requests from controller directly in secchan.

With in-band control, it can happen that the controller needs to send
out an ARP request to find out the MAC address of the switch.  These
packets are sent as broadcasts, so the secure channel will attempt to
send them back to the controller as ofp_packet_in messages.  Of course,
that won't work, because the controller won't be able to respond to
the ofp_packet_in (because it needs the MAC address of the switch to
do so).

This commit makes the secure channel recognize broadcast ARP packets
that originate from the controller and flood them without passing them
back up to the controller.
---
 secchan/secchan.c | 60 +++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 58 insertions(+), 2 deletions(-)

diff --git a/secchan/secchan.c b/secchan/secchan.c
index 4fb4eac5..8c59b8ae 100644
--- a/secchan/secchan.c
+++ b/secchan/secchan.c
@@ -103,6 +103,9 @@ static struct mac_learning *local_ml;
 /* -f, --fail: Behavior when the connection to the controller fails. */
 static enum fail_mode fail_mode = FAIL_OPEN;
 
+/* The OpenFlow virtual network device ofX. */
+static struct netdev *of_device;
+
 /* --inactivity-probe: Number of seconds without receiving a message from the
    controller before sending an inactivity probe. */
 static int probe_interval = 15;
@@ -129,7 +132,6 @@ int
 main(int argc, char *argv[])
 {
     struct vconn *listen_vconn;
-    struct netdev *of_device;
     struct relay *controller_relay;
     const char *nl_name;
     char of_name[16];
@@ -184,7 +186,6 @@ main(int argc, char *argv[])
         } else {
             error(retval, "Could not get flags for %s device", of_name);
         }
-        netdev_close(of_device);
     } else {
         error(retval, "Could not open %s device", of_name);
     }
@@ -366,6 +367,56 @@ relay_destroy(struct relay *r)
     free(r);
 }
 
+static bool
+is_controller_mac(const uint8_t dl_addr[ETH_ADDR_LEN],
+                  struct rconn *controller) 
+{
+    static uint32_t ip, last_nonzero_ip;
+    static uint8_t mac[ETH_ADDR_LEN], last_nonzero_mac[ETH_ADDR_LEN];
+    static time_t next_refresh = 0;
+
+    uint32_t last_ip = ip;
+
+    time_t now = time(0);
+
+    ip = rconn_get_ip(controller);
+    if (last_ip != ip || !next_refresh || now >= next_refresh) {
+        bool have_mac;
+
+        /* Look up MAC address. */
+        memset(mac, 0, sizeof mac);
+        if (ip) {
+            int retval = netdev_arp_lookup(of_device, ip, mac);
+            if (retval) {
+                VLOG_DBG("cannot look up controller hw address ("IP_FMT"): %s",
+                         IP_ARGS(&ip), strerror(retval));
+            }
+        }
+        have_mac = !eth_addr_is_zero(mac);
+
+        /* Log changes in IP, MAC addresses. */
+        if (ip && ip != last_nonzero_ip) {
+            VLOG_DBG("controller IP address changed from "IP_FMT
+                     " to "IP_FMT, IP_ARGS(&last_nonzero_ip), IP_ARGS(&ip));
+            last_nonzero_ip = ip;
+        }
+        if (have_mac && memcmp(last_nonzero_mac, mac, ETH_ADDR_LEN)) {
+            VLOG_DBG("controller MAC address changed from "ETH_ADDR_FMT" to "
+                     ETH_ADDR_FMT,
+                     ETH_ADDR_ARGS(last_nonzero_mac), ETH_ADDR_ARGS(mac));
+            memcpy(last_nonzero_mac, mac, ETH_ADDR_LEN);
+        }
+
+        /* Schedule next refresh.
+         *
+         * If we have an IP address but not a MAC address, then refresh
+         * quickly, since we probably will get a MAC address soon (via ARP).
+         * Otherwise, we can afford to wait a little while. */
+        next_refresh = now + (!ip || have_mac ? 10 : 1);
+    }
+    return !eth_addr_is_zero(mac) && eth_addr_equals(mac, dl_addr);
+}
+
 static bool
 local_hook(struct relay *r)
 {
@@ -409,6 +460,11 @@ local_hook(struct relay *r)
             VLOG_DBG("learned that "ETH_ADDR_FMT" is on port %"PRIu16,
                      ETH_ADDR_ARGS(flow.dl_src), in_port);
         }
+    } else if (flow.dl_type == htons(ETH_TYPE_ARP)
+               && eth_addr_is_broadcast(flow.dl_dst)
+               && is_controller_mac(flow.dl_src,
+                                    r->halves[HALF_REMOTE].rconn)) {
+        out_port = OFPP_FLOOD;
     } else {
         return false;
     }
-- 
2.30.2