If sending on the arp fd fails, then re-open the arp fd and restore arp

state to what it was before closing the fd.  It may allow the client to
continue working in the face of error, as arp functionality is not critical
for simply holding a lease.

ndhc/arp.c

@@ -1,5 +1,5 @@
 /* arp.c - arp ping checking
- * Time-stamp: <2011-07-04 20:49:18 njk>
+ * Time-stamp: <2011-07-04 22:32:29 njk>
  *
  * Copyright 2010-2011 Nicholas J. Kain <njkain@gmail.com>
  *
@@ -181,6 +181,44 @@ out:
     return -1;
 }
 
+static void arp_switch_state(struct client_state_t *cs, arp_state_t state)
+{
+    arp_state_t prev_state = arpState;
+    log_line("DEBUG: arp_switch_state: called.");
+    if (arpState == state || arpState >= AS_MAX)
+        return;
+    log_line("DEBUG: arp_switch_state: passed valid state change test");
+    arpState = state;
+    arp_stats[arpState].ts = 0;
+    arp_stats[arpState].count = 0;
+    log_line("DEBUG: arp_switch_state: state = %u", state);
+    if (arpState == AS_NONE) {
+        arp_close_fd(cs);
+        return;
+    }
+    if (cs->arpFd == -1) {
+        log_line("DEBUG: arp_switch_state: opening arpFd");
+        if (arp_open_fd(cs) == -1)
+            suicide("arp: failed to open arpFd when changing state to %u",
+                    arpState);
+        log_line("DEBUG: arp_switch_state: opened arpFd");
+        if (arpState != AS_DEFENSE)
+            arp_set_bpf_basic(cs->arpFd);
+        log_line("DEBUG: arp_switch_state: installed filters");
+    }
+    if (arpState == AS_DEFENSE) {
+        log_line("DEBUG: arp_switch_state: changed to DEFENSE filter");
+        arp_set_bpf_defense(cs, cs->arpFd);
+        return;
+    }
+    if (prev_state == AS_DEFENSE) {
+        log_line("DEBUG: arp_switch_state: removed DEFENSE filter");
+        arp_set_bpf_basic(cs->arpFd);
+        return;
+    }
+    log_line("DEBUG: arp_switch_state: leaving.");
+}
+
 int arp_close_fd(struct client_state_t *cs)
 {
     if (cs->arpFd == -1)
@@ -192,6 +230,19 @@ int arp_close_fd(struct client_state_t *cs)
     return 1;
 }
 
+static int arp_reopen_fd(struct client_state_t *cs)
+{
+    arp_state_t prev_state = arpState;
+    arp_close_fd(cs);
+    if (arp_open_fd(cs) == -1) {
+        log_warning("arp_reopen_fd: Failed to open.  Something is very wrong.");
+        log_warning("arp_reopen_fd: Client will still run, but functionality will be degraded.");
+        return -1;
+    }
+    arp_switch_state(cs, prev_state);
+    return 0;
+}
+
 static int arp_send(struct client_state_t *cs, struct arpMsg *arp)
 {
     struct sockaddr_ll addr = {
@@ -201,10 +252,15 @@ static int arp_send(struct client_state_t *cs, struct arpMsg *arp)
     };
     memcpy(addr.sll_addr, client_config.arp, 6);
 
+    if (cs->arpFd == -1) {
+        log_warning("arp_send: Send attempted when no ARP fd is open.");
+        return -1;
+    }
+
     if (safe_sendto(cs->arpFd, (const char *)arp, sizeof *arp,
                     0, (struct sockaddr *)&addr, sizeof addr) < 0) {
         log_error("arp: sendto failed: %s", strerror(errno));
-        arp_close_fd(cs);
+        arp_reopen_fd(cs);
         return -1;
     }
     arp_stats[arpState].count++;
@@ -253,44 +309,6 @@ static void arpreply_clear()
     arpreply_offset = 0;
 }
 
-static void arp_switch_state(struct client_state_t *cs, arp_state_t state)
-{
-    arp_state_t prev_state = arpState;
-    log_line("DEBUG: arp_switch_state: called.");
-    if (arpState == state || arpState >= AS_MAX)
-        return;
-    log_line("DEBUG: arp_switch_state: passed valid state change test");
-    arpState = state;
-    arp_stats[arpState].ts = 0;
-    arp_stats[arpState].count = 0;
-    log_line("DEBUG: arp_switch_state: state = %u", state);
-    if (arpState == AS_NONE) {
-        arp_close_fd(cs);
-        return;
-    }
-    if (cs->arpFd == -1) {
-        log_line("DEBUG: arp_switch_state: opening arpFd");
-        if (arp_open_fd(cs) == -1)
-            suicide("arp: failed to open arpFd when changing state to %u",
-                    arpState);
-        log_line("DEBUG: arp_switch_state: opened arpFd");
-        if (arpState != AS_DEFENSE)
-            arp_set_bpf_basic(cs->arpFd);
-        log_line("DEBUG: arp_switch_state: installed filters");
-    }
-    if (arpState == AS_DEFENSE) {
-        log_line("DEBUG: arp_switch_state: changed to DEFENSE filter");
-        arp_set_bpf_defense(cs, cs->arpFd);
-        return;
-    }
-    if (prev_state == AS_DEFENSE) {
-        log_line("DEBUG: arp_switch_state: removed DEFENSE filter");
-        arp_set_bpf_basic(cs->arpFd);
-        return;
-    }
-    log_line("DEBUG: arp_switch_state: leaving.");
-}
-
 // Callable from DS_SELECTING, DS_RENEWING, or DS_REBINDING via an_packet()
 int arp_check(struct client_state_t *cs, struct dhcpmsg *packet)
 {
@@ -305,7 +323,7 @@ int arp_check(struct client_state_t *cs, struct dhcpmsg *packet)
     return 0;
 }
 
-// Callable only from DS_BOUND via netlink.c:nl_process_msgs().
+// Callable only from DS_BOUND via state.c:ifup_action().
 int arp_gw_check(struct client_state_t *cs)
 {
     arp_switch_state(cs, AS_GW_CHECK);
@@ -554,8 +572,7 @@ void handle_arp_response(struct client_state_t *cs)
         log_line("DEBUG: TODO actually do work!");
         break;
     default:
-        log_error("handle_arp_response: called in invalid state 0x%02x",
+        log_error("handle_arp_response: called in invalid state %u", arpState);
-                  cs->dhcpState);
         arp_close_fd(cs);
     }
     log_line("DEBUG: Leaving handle_arp_response.");