The Linux PXE server (http://www.kano.org.uk/projects/pxe) does not
set the server identifier in its ProxyDHCP responses. If the server
ID is missing, do not treat this as an error.
This resolves the "vague and unsettling memory" mentioned in commit
fdb8481d ("[dhcp] Verify server identifier on ProxyDHCPACKs").
Note that we already accept ProxyDHCPOFFERs without a server
identifier; they get treated as potential BOOTP packets.
Settings can be constructed using a dotted-decimal notation, to allow
for access to unnamed settings. The default interpretation is as a
DHCP option number (with encapsulated options represented as
"<encapsulating option>.<encapsulated option>".
In several contexts (e.g. SMBIOS, Phantom CLP), it is useful to
interpret the dotted-decimal notation as referring to non-DHCP
options. In this case, it becomes necessary for these contexts to
ignore standard DHCP options, otherwise we end up trying to, for
example, retrieve the boot filename from SMBIOS.
Allow settings blocks to specify a "tag magic". When dotted-decimal
notation is used to construct a setting, the tag magic value of the
originating settings block will be ORed in to the tag number.
Store/fetch methods can then check for the magic number before
interpreting arbitrarily-numbered settings.
The ProxyDHCPREQUEST is a unicast packet, so the first request will
almost always be lost due to not having the IP address in the ARP
cache. If the minimum retry time is set to one second (as per commit
ff2b6a5), then ProxyDHCP will time out and give up before managing to
successfully transmit a request.
The DHCP timers need to be reworked anyway, so this mild hack is
acceptable for now.
New min_timeout and max_timeout fields in struct retry_timer allow
users of this timer to set their own desired minimum and maximum
timeouts, without being constrained to a single global minimum and
maximum. Users of the timer can still elect to use the default global
values by leaving the min_timeout and max_timeout fields as 0.
Altiris erroneously cares about the ordering of DHCP options, and will
get confused if we don't construct them in the order it expects.
This is observed (so far) only when attempting to deploy 64-bit Win2k3.
Verifying server ID and DHCP transaction ID is insufficient to
differentiate between DHCPACK and ProxyDHCPACK when the DHCP server and
Proxy DHCP server are the same machine.
Perform the same test for a matching DHCP_SERVER_IDENTIFIER on
ProxyDHCPACKs as we do for DHCPACKs. Otherwise, a retransmitted
DHCPACK can end up being treated as the ProxyDHCPACK.
I have a vague and unsettling memory that this test was deliberately
omitted, but I can't remember why, and can't find anything in the VC
logs.
A missing test for dhcp->dhcpoffer in dhcp_timer_expired() was causing
the client to transition to DHCPREQUEST after timing out on waiting
for ProxyDHCP even if no DHCPOFFERs had been received.
The PXE spec is (as usual) unclear on precisely when ProxyDHCPREQUESTs
should be issued. We adapt the following, slightly paranoid approach:
If an offer contains an IP address, then it is a normal DHCPOFFER.
If an offer contains an option #60 "PXEClient", then it is a
ProxyDHCPOFFER. Note that the same packet can be both a normal
DHCPOFFER and a ProxyDHCPOFFER.
After receiving the normal DHCPACK, if we have received a
ProxyDHCPOFFER, we unicast a ProxyDHCPREQUEST back to the ProxyDHCP
server on port 4011. If we time out waiting for a ProxyDHCPACK, we
treat this as a non-fatal error.
Allow for settings to be described by something other than a DHCP option
tag if desirable. Currently used only for the MAC address setting.
Separate out fake DHCP packet creation code from dhcp.c to fakedhcp.c.
Remove notion of settings from dhcppkt.c.
Rationalise dhcp.c to use settings API only for final registration of the
DHCP options, rather than using {store,fetch}_setting throughout.
Add dedicated functions create_dhcpdiscover(), create_dhcpack() and
create_proxydhcpack() for use by external code such as the PXE preboot
code.
Register ProxyDHCP options under the global scope "proxydhcp".
Unregister previously-acquired DHCP and ProxyDHCP settings when DHCP
succeeds.
RFC 4390 provides for the DHCP client identifier to contain the link-layer
hardware type and MAC address when the MAC address exceeds 16 bytes.
However, the hardware type field is only 8 bits; we were assuming 16 bits.
