Merge pull request #366 from dpino/ndp-without-timers

Do not use timers to implement NS requests and retries

src/apps/lwaftr/ipv6_apps.lua

@@ -165,62 +165,55 @@ function Fragmenter:push ()
    end
 end
 
-local NS_RESOLVE_THRESHOLD = 5 -- Time limit to resolve IPv6 addr to MAC.
-
--- TODO: handle any NS retry policy code here
 function NDP:new(conf)
    local o = setmetatable({}, {__index=NDP})
    o.conf = conf
    -- TODO: verify that the src and dst ipv6 addresses and src mac address
    -- have been provided, in pton format.
    if not conf.dst_eth then
-      o.do_ns_request = true
+      self.ns_pkt = ndp.form_ns(conf.src_eth, conf.src_ipv6, conf.dst_ipv6)
+      self.ns_interval = 3 -- Send a new NS every three seconds.
+      self.ns_max_retries = 5 -- Max number of NS retries.
+      self.ns_retries = 0
    end
    o.dst_eth = conf.dst_eth -- Intentionally nil if to request by NS
    return o
 end
 
+function NDP:maybe_send_ns_request (output)
+   if self.dst_eth then return end
+   if self.ns_retries == self.ns_max_retries then
+      error(("Could not resolve IPv6 address: %s"):format(
+         ipv6:ntop(self.conf.dst_ipv6)))
+   end
+   self.next_ns_time = self.next_ns_time or engine.now()
+   if self.next_ns_time <= engine.now() then
+      self:send_ns(output)
+      self.next_ns_time = engine.now() + self.ns_interval
+      self.ns_retries = self.ns_retries + 1
+   end
+end
+
+function NDP:send_ns (output)
+   transmit(output, packet.clone(self.ns_pkt))
+end
+
 function NDP:push()
    local isouth, osouth = self.input.south, self.output.south
    local inorth, onorth = self.input.north, self.output.north
-   if self.do_ns_request then
-      self.do_ns_request = false
-      local ns_pkt = ndp.form_ns(self.conf.src_eth, self.conf.src_ipv6,
-         self.conf.dst_ipv6)
-      -- Send a NS packet inmediately.
-      transmit(osouth, packet.clone(ns_pkt))
-
-      -- Send a new NS packet after every second.
-      timer.activate(timer.new("retry_ns",
-                               function ()
-                                 transmit(osouth, packet.clone(ns_pkt))
-                               end,
-                               1e9,
-                               "repeating"))
-
-      -- Abort execution if NS_RESOLVE_THRESHOLD expires.
-      local function abort()
-         error(("Could not resolve IPv6 address: %s"):format(
-            ipv6:ntop(self.conf.dst_ipv6)))
-         main.exit(1)
-      end
-      timer.activate(timer.new("retry_ns_threshold",
-                               abort,
-                               NS_RESOLVE_THRESHOLD * 1e9))
 
-      -- TODO: do unsolicited neighbor advertisement on start and on
-      -- configuration reloads?
-      -- This would be an optimization, not a correctness issue
-   end
+   -- TODO: do unsolicited neighbor advertisement on start and on
+   -- configuration reloads?
+   -- This would be an optimization, not a correctness issue
+   self:maybe_send_ns_request(osouth)
+
    for _=1,link.nreadable(isouth) do
       local p = receive(isouth)
       if ndp.is_ndp(p) then
          if not self.dst_eth and ndp.is_solicited_neighbor_advertisement(p) then
             local dst_ethernet = ndp.get_dst_ethernet(p, {self.conf.dst_ipv6})
             if dst_ethernet then
                self.dst_eth = dst_ethernet
-               timer.deactivate("retry_ns_threshold")
-               timer.deactivate("retry_ns")
             end
             packet.free(p)
          elseif ndp.is_neighbor_solicitation_for_addr(p, self.conf.src_ipv6) then

src/core/timer.lua

@@ -75,17 +75,6 @@ local function is_timer (t)
    return type(t) == "table" and (t.name and t.fn and t.ticks)
 end
 
-function deactivate (timer_or_name)
-   local name = timer_or_name
-   if is_timer(timer_or_name) then
-      name = timer_or_name.name
-   end
-   assert(type(name) == "string", "Incorrect value. Timer name expected")
-   local tick, pos = find_timer(name)
-   if not tick then return end
-   table.remove(timers[tick], pos)
-end
-
 function new (name, fn, nanos, mode)
    return { name = name,
             fn = fn,
@@ -96,11 +85,6 @@ end
 function selftest ()
    print("selftest: timer")
 
-   -- Test deactivate.
-   local t = new("timer", function() end, 1e6)
-   activate(t)
-   deactivate(t)
-
    ticks = 0
    local ntimers, runtime = 10000, 100000
    local count, expected_count = 0, 0