| From 566e20e7740d8f032614c47b93c866a1d2c97840 Mon Sep 17 00:00:00 2001 |
| From: Paul Stewart <pstew@chromium.org> |
| Date: Mon, 14 Jun 2021 12:32:58 +0000 |
| Subject: [PATCH 15/19] Ensure gateway probe is broadcast |
| |
| The arp_new() method does not always return a freshly |
| initialized arp_state structure. For example, if |
| dhcp_probe_gw() is called while a probe from |
| start_unicast_arp() is still running, the arp_state |
| object from the unicast ARP call will be returned by |
| arp_new(). This can happen when a DHCP renew succeeds |
| while a unicast "GatewayArp" is still in progress. |
| |
| In the above scenario we need to make sure the dest_hwlen |
| field of the arp_state structure is zero. This signals a |
| broadcast ARP, and will ensure that the callbacks that are |
| invoked by the ARP state machine know which case we are in. |
| |
| While here, add a small optimization that skips a |
| broadcast gateway ARP if a unicast ARP succeeds. |
| |
| BUG=chromium:531042 |
| TEST=Reconnect to WiFi network where ARP fails |
| --- |
| src/dhcp.c | 4 ++++ |
| 1 file changed, 4 insertions(+) |
| |
| diff --git a/src/dhcp.c b/src/dhcp.c |
| index c8ec40da..ac339a6a 100644 |
| --- a/src/dhcp.c |
| +++ b/src/dhcp.c |
| @@ -2171,6 +2171,8 @@ dhcp_probe_gw_response(struct arp_state *astate, const struct arp_msg *amsg) |
| if (astate->dest_hwlen) { |
| /* Response to unicast ARP. */ |
| rpc_notify_unicast_arp(astate->iface); |
| + /* Unicast ARP succeeded; no need for broadcast ARP. */ |
| + astate->iface->options->options &= ~DHCPCD_ARPGW; |
| } else { |
| /* Response to arpgw request. */ |
| save_gateway_addr(astate->iface, amsg->sha); |
| @@ -2199,6 +2201,8 @@ dhcp_probe_gw(struct interface *ifp) |
| state->offer, state->offer_len, DHO_ROUTER) == 0) { |
| astate = arp_new(ifp, &gateway_addr); |
| if (astate) { |
| + /* Make sure we're doing a broadcast ARP. */ |
| + astate->dest_hwlen = 0; |
| astate->src_addr.s_addr = state->offer->yiaddr; |
| astate->probed_cb = dhcp_probe_gw_timeout; |
| astate->conflicted_cb = dhcp_probe_gw_response; |
| -- |
| 2.33.0.800.g4c38ced690-goog |
| |
