From 29a1c7892c61d863a5c444040cc24b6dc1bc812c Mon Sep 17 00:00:00 2001
From: Mukesh Agrawal <quiche@chromium.org>
Date: Mon, 31 May 2021 13:29:34 +0000
Subject: [PATCH 05/19] Be more permissive on NAKs

Previously, we'd reject NAKs that did not include a server ID.
Since we'd only check that a server ID was present, but did not
validate it against any stored state, the test is merely pedantic.
Moreover, some DHCP servers (e.g. OpenBSD 4.6) send NAK messages
without a server ID. [1]

To improve compatibility with real-world DHCP servers, drop the
check for the presence of a server ID.

BUG=chrome-os-partner:27930
TEST=network_DhcpNak

[1] http://openbsd.7691.n7.nabble.com/dhcpd-omits-server-id-option-54-in-NAK-to-a-RENEW-request-td41044.html

Reviewed-on: https://chromium-review.googlesource.com/194972
---
 src/dhcp.c | 9 ---------
 1 file changed, 9 deletions(-)

diff --git a/src/dhcp.c b/src/dhcp.c
index 1ff59a1a..4590958c 100644
--- a/src/dhcp.c
+++ b/src/dhcp.c
@@ -3266,15 +3266,6 @@ dhcp_handledhcp(struct interface *ifp, struct bootp *bootp, size_t bootp_len,
 	}
 
 	if (type == DHCP_NAK) {
-		/* For NAK, only check if we require the ServerID */
-		if (has_option_mask(ifo->requiremask, DHO_SERVERID) &&
-		    get_option_addr(ifp->ctx, &addr,
-		    bootp, bootp_len, DHO_SERVERID) == -1)
-		{
-			LOGDHCP(logwarnx, "reject NAK");
-			return;
-		}
-
 		/* We should restart on a NAK */
 		LOGDHCP(logwarnx, "NAK:");
 		if ((msg = get_option_string(ifp->ctx,
-- 
2.33.0.800.g4c38ced690-goog