В Tue, 22 Apr 2014 00:13:15 +0000 "Mroczek, Joseph T" <joseph.t.mroc...@intel.com> пишет:
> > From: Andrey Borzenkov [mailto:arvidj...@gmail.com] > > Sent: Monday, April 21, 2014 10:42 AM > > > > В Mon, 21 Apr 2014 15:56:07 +0000 > > "Mroczek, Joseph T" <joseph.t.mroc...@intel.com> пишет: > > > > > > > From: Behalf Of Vladimir 'f-coder/phcoder' Serbinenko On 19.04.2014 > > > > 02:48, Mroczek, Joseph T wrote: > > > > > Hello: > > > > > > > > > > Currently, the DHCP logic assumes that if a gateway is received in > > > > > the DHCP > > > > packet the boot server is on a remote network. Given that CIDR is > > > > now over > > > > 20 years old, I think it is a safe assumption that a netmask will be > > > > offered in DHCP options. > > > > > > > > > > Can this be removed? Or is there still a need to cover the classful > > > > > case? > > > > > > > > > Please detail the failure scenario. > > > > Current code follows standard behaviour for PXE clients and changing > > > > it would break any installation which relies on it. > > > > > > > Hmm ... re-reading RFC2131 I ask myself what are conditions when > > *client* is supposed to use gateway_ip at all. According to RFC, giaddr is > > set > > by DHCP relay when it forwards request from client so server knows where > > to send reply to. DHCP relay then forwards reply on local subnet according > > to > > standard rules. RFC does not say anything about client usage of this field. > > Actually there is no requirement that DHCP relay also functions as normal > > router. > > Use of giaddr as a gateway dates back to RFC951. At that point in time we did > not have DHCP options, so this was a way to dynamicially learn the gateway. > Oh. Digging further, RFC1542 quite explicitly states the same: A BOOTP client MUST NOT interpret the 'giaddr' field of a BOOTREPLY message to be the IP address of an IP router. A BOOTP client SHOULD completely ignore the contents of the 'giaddr' field in BOOTREPLY messages. ... > > > > The failure will occur in most if not all cases where the DHCP sends a > > > gateway when the boot server is on the same subnet as the client, > > > > In view of the above, how is it possible? DHCP server is not supposed to set > > this field at all - at the most it simply replies back to relay with same > > value of > > giaddr it got. If giaddr is set it is already indication that server and > > client are on > > different subnets. > > For my case, DHCP server is on different subnet but boot/TFTP server is on > same as client. > I see. I rather agree with your patch, it looks like semantic of giaddr was settled 20 years ago. _______________________________________________ Grub-devel mailing list Grub-devel@gnu.org https://lists.gnu.org/mailman/listinfo/grub-devel
