[gPXE-devel] [PATCH]: dhcp: Don't ignore duplicate offers when the dups differ by PXE options presence

[Gianni Tedesco]

This fixes a regression against Altiris Rapideploy. During the DHCP
discover stage the Rapideploy server sends a relayed offer without PXE
options, a non-relayed offer without PXE and then a non-relayed offer
with PXE. This is a regression from the 0.9.6 days before
9119b0c8af15333796e02433677a54e952b1a73d and before ignoring duplicate
DHCP offers. This regression causes the state-machine not to enter the
proxyDHCP state and therefore prevents the PXEClient server list and
menu from being retrieved which, in turn, prevents the boot ROM from
operating as expected.

My proposed solution is to not consider offers duplicate if they differ
in the presence or absence of PXEClient boot options.

Without this patch the afore-mentioned sequence of DHCP offers resulted
in (OFFER, dup, dup) sequence, whereas with the patch, it results in
(OFFER, dup, PXE-OFFER) sequence as expected. That is enough to tweak
the state machine in to entering the ProxyDHCP state.

Signed-off-by: Gianni Tedesco <gianni.tedesco at citrix.com>

diff --git a/src/net/udp/dhcp.c b/src/net/udp/dhcp.c
index 4bfcb80..2e10643 100644
--- a/src/net/udp/dhcp.c
+++ b/src/net/udp/dhcp.c
@@ -412,25 +412,6 @@ static void dhcp_rx_offer ( struct dhcp_session *dhcp,
        if ( dhcppkt->dhcphdr->yiaddr.s_addr )
                DBGC ( dhcp, " for %s", inet_ntoa ( dhcppkt->dhcphdr->yiaddr ));
 
-       /* Enqueue an offer to be filled in */
-       for ( i = 0 ; i < DHCP_MAX_OFFERS ; i++ ) {
-               if ( ! dhcp->offers[i].valid )
-                       break;
-
-               if ( dhcp->offers[i].server.s_addr == server_id.s_addr ) {
-                       DBGC ( dhcp, " dup\n" );
-                       return;
-               }
-       }
-       if ( i == DHCP_MAX_OFFERS ) {
-               DBGC ( dhcp, " dropped\n" );
-               return;
-       }
-
-       offer = &dhcp->offers[i];
-       offer->server = server_id;
-       offer->ip = dhcppkt->dhcphdr->yiaddr;
-
        /* Identify "PXEClient" vendor class */
        vci_len = dhcppkt_fetch ( dhcppkt, DHCP_VENDOR_CLASS_ID,
                                  vci, sizeof ( vci ) );
@@ -466,6 +447,29 @@ static void dhcp_rx_offer ( struct dhcp_session *dhcp,
                   the provided filename */
                has_pxeopts = has_pxeopts || ( discovery_control & PXEBS_SKIP );
        }
+
+       /* Enqueue an offer to be filled in */
+       for ( i = 0 ; i < DHCP_MAX_OFFERS ; i++ ) {
+               if ( ! dhcp->offers[i].valid )
+                       break;
+
+               if ( dhcp->offers[i].server.s_addr == server_id.s_addr ) {
+            if ( (has_pxeclient && has_pxeopts) ==
+                !!(dhcp->offers[i].valid & DHCP_OFFER_PXE) ) {
+                               DBGC ( dhcp, " dup\n" );
+                    return;
+            }
+               }
+       }
+       if ( i == DHCP_MAX_OFFERS ) {
+               DBGC ( dhcp, " dropped\n" );
+               return;
+       }
+
+       offer = &dhcp->offers[i];
+       offer->server = server_id;
+       offer->ip = dhcppkt->dhcphdr->yiaddr;
+
        if ( has_pxeclient )
                DBGC ( dhcp, "%s", ( has_pxeopts ? " pxe" : " proxy" ) );