diff --git a/server/CommandListener.cpp b/server/CommandListener.cpp
index b3ff9ca..d858e60 100644
--- a/server/CommandListener.cpp
+++ b/server/CommandListener.cpp
@@ -1733,12 +1733,15 @@
         const char* destination = argv[nextArg++];
         const char* nexthop = argc > nextArg ? argv[nextArg] : NULL;
 
+        int ret;
         if (add) {
-            if (!sNetCtrl->addRoute(netId, interface, destination, nexthop, legacy, uid)) {
-                return operationError(client, "addRoute() failed");
-            }
-        } else if (!sNetCtrl->removeRoute(netId, interface, destination, nexthop, legacy, uid)) {
-            return operationError(client, "removeRoute() failed");
+            ret = sNetCtrl->addRoute(netId, interface, destination, nexthop, legacy, uid);
+        } else {
+            ret = sNetCtrl->removeRoute(netId, interface, destination, nexthop, legacy, uid);
+        }
+        if (ret != 0) {
+            errno = -ret;
+            return operationError(client, add ? "addRoute() failed" : "removeRoute() failed");
         }
 
         return success(client);
diff --git a/server/NetworkController.cpp b/server/NetworkController.cpp
index f5739e9..de433b7 100644
--- a/server/NetworkController.cpp
+++ b/server/NetworkController.cpp
@@ -345,13 +345,13 @@
     return status;
 }
 
-bool NetworkController::addRoute(unsigned netId, const char* interface, const char* destination,
-                                 const char* nexthop, bool legacy, unsigned uid) {
+int NetworkController::addRoute(unsigned netId, const char* interface, const char* destination,
+                                const char* nexthop, bool legacy, unsigned uid) {
     return modifyRoute(netId, interface, destination, nexthop, true, legacy, uid);
 }
 
-bool NetworkController::removeRoute(unsigned netId, const char* interface, const char* destination,
-                                    const char* nexthop, bool legacy, unsigned uid) {
+int NetworkController::removeRoute(unsigned netId, const char* interface, const char* destination,
+                                   const char* nexthop, bool legacy, unsigned uid) {
     return modifyRoute(netId, interface, destination, nexthop, false, legacy, uid);
 }
 
@@ -364,18 +364,16 @@
     return mValidNetworks.find(netId) != mValidNetworks.end();
 }
 
-bool NetworkController::modifyRoute(unsigned netId, const char* interface, const char* destination,
-                                    const char* nexthop, bool add, bool legacy, unsigned uid) {
+int NetworkController::modifyRoute(unsigned netId, const char* interface, const char* destination,
+                                   const char* nexthop, bool add, bool legacy, unsigned uid) {
     if (!isValidNetwork(netId)) {
         ALOGE("invalid netId %u", netId);
-        errno = EINVAL;
-        return false;
+        return -EINVAL;
     }
 
     if (getNetworkId(interface) != netId) {
         ALOGE("netId %u has no such interface %s", netId, interface);
-        errno = ENOENT;
-        return false;
+        return -ENOENT;
     }
 
     RouteController::TableType tableType;
diff --git a/server/NetworkController.h b/server/NetworkController.h
index 30c9142..4e93fa1 100644
--- a/server/NetworkController.h
+++ b/server/NetworkController.h
@@ -67,10 +67,10 @@
 
     // Routes are added to tables determined by the interface, so only |interface| is actually used.
     // |netId| is given only to sanity check that the interface has the correct netId.
-    bool addRoute(unsigned netId, const char* interface, const char* destination,
-                  const char* nexthop, bool legacy, unsigned uid);
-    bool removeRoute(unsigned netId, const char* interface, const char* destination,
-                     const char* nexthop, bool legacy, unsigned uid);
+    int addRoute(unsigned netId, const char* interface, const char* destination,
+                 const char* nexthop, bool legacy, unsigned uid);
+    int removeRoute(unsigned netId, const char* interface, const char* destination,
+                    const char* nexthop, bool legacy, unsigned uid);
 
     bool isValidNetwork(unsigned netId) const;
 
@@ -79,8 +79,8 @@
     typedef std::multimap<unsigned, std::string>::iterator InterfaceIterator;
     typedef std::pair<InterfaceIterator, InterfaceIterator> InterfaceRange;
 
-    bool modifyRoute(unsigned netId, const char* interface, const char* destination,
-                     const char* nexthop, bool add, bool legacy, unsigned uid);
+    int modifyRoute(unsigned netId, const char* interface, const char* destination,
+                    const char* nexthop, bool add, bool legacy, unsigned uid);
 
     struct UidEntry {
         int uid_start;
diff --git a/server/RouteController.cpp b/server/RouteController.cpp
index 3c16fa3..9716b9e 100644
--- a/server/RouteController.cpp
+++ b/server/RouteController.cpp
@@ -309,7 +309,10 @@
                             mask.intValue, NULL);
 }
 
-bool modifyRoute(const char* interface, const char* destination, const char* nexthop,
+// Adds or removes an IPv4 or IPv6 route to the specified table and, if it's directly-connected
+// route, to the main table as well.
+// Returns 0 on success or negative errno on failure.
+int modifyRoute(const char* interface, const char* destination, const char* nexthop,
                  int action, RouteController::TableType tableType, unsigned /* uid */) {
     uint32_t table = 0;
     switch (tableType) {
@@ -329,26 +332,27 @@
         }
     }
     if (!table) {
-        return false;
+        return -ESRCH;
     }
 
-    if (modifyIpRoute(action, table, interface, destination, nexthop)) {
-        return false;
+    int ret = modifyIpRoute(action, table, interface, destination, nexthop);
+    if (ret != 0) {
+        return ret;
     }
 
     // If there's no nexthop, this is a directly connected route. Add it to the main table also, to
-    // let the kernel find it when validating nexthops when global routes are added. Don't do this
-    // for IPv6, since all directly-connected routes in v6 are link-local and should already be in
-    // the main table.
-    // TODO: A failure here typically means that the route already exists in the main table, so we
-    // ignore it. It's wrong to ignore other kinds of failures, but we have no way to distinguish
-    // them based on the return status of the 'ip' command. Fix this situation by ignoring errors
-    // only when action == ADD && error == EEXIST.
-    if (!nexthop && !strchr(destination, ':')) {
-        modifyIpRoute(action, RT_TABLE_MAIN, interface, destination, NULL);
+    // let the kernel find it when validating nexthops when global routes are added.
+    if (!nexthop) {
+        ret = modifyIpRoute(action, RT_TABLE_MAIN, interface, destination, NULL);
+        // A failure with action == ADD && errno == EEXIST means that the route already exists in
+        // the main table, perhaps because the kernel added it automatically as part of adding the
+        // IP address to the interface. Ignore this, but complain about everything else.
+        if (ret != 0 && !(action == RTM_NEWROUTE && ret == -EEXIST)) {
+            return ret;
+        }
     }
 
-    return true;
+    return 0;
 }
 
 bool flushRoutes(const char* interface) {
@@ -450,12 +454,12 @@
     return modifyDefaultNetworkRules(interface, permission, DEL);
 }
 
-bool RouteController::addRoute(const char* interface, const char* destination,
-                               const char* nexthop, TableType tableType, unsigned uid) {
+int RouteController::addRoute(const char* interface, const char* destination,
+                              const char* nexthop, TableType tableType, unsigned uid) {
     return modifyRoute(interface, destination, nexthop, RTM_NEWROUTE, tableType, uid);
 }
 
-bool RouteController::removeRoute(const char* interface, const char* destination,
-                                  const char* nexthop, TableType tableType, unsigned uid) {
+int RouteController::removeRoute(const char* interface, const char* destination,
+                                 const char* nexthop, TableType tableType, unsigned uid) {
     return modifyRoute(interface, destination, nexthop, RTM_DELROUTE, tableType, uid);
 }
diff --git a/server/RouteController.h b/server/RouteController.h
index 7292579..4695a6c 100644
--- a/server/RouteController.h
+++ b/server/RouteController.h
@@ -41,10 +41,10 @@
     static bool addToDefaultNetwork(const char* interface, Permission permission);
     static bool removeFromDefaultNetwork(const char* interface, Permission permission);
 
-    static bool addRoute(const char* interface, const char* destination, const char* nexthop,
-                         TableType tableType, unsigned uid);
-    static bool removeRoute(const char* interface, const char* destination, const char* nexthop,
-                            TableType tableType, unsigned uid);
+    static int addRoute(const char* interface, const char* destination, const char* nexthop,
+                        TableType tableType, unsigned uid);
+    static int removeRoute(const char* interface, const char* destination, const char* nexthop,
+                           TableType tableType, unsigned uid);
 };
 
 #endif  // NETD_SERVER_ROUTE_CONTROLLER_H