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Message-ID: <20120812140511.GC6003@redhat.com> Date: Sun, 12 Aug 2012 17:05:12 +0300 From: "Michael S. Tsirkin" <mst@...hat.com> To: Or Gerlitz <or.gerlitz@...il.com> Cc: "Eric W. Biederman" <ebiederm@...ssion.com>, Ali Ayoub <ali@...lanox.com>, David Miller <davem@...emloft.net>, ogerlitz@...lanox.com, roland@...nel.org, netdev@...r.kernel.org, sean.hefty@...el.com, erezsh@...lanox.co.il, dledford@...hat.com Subject: Re: [PATCH V2 09/12] net/eipoib: Add main driver functionality On Thu, Aug 09, 2012 at 07:06:46AM +0300, Or Gerlitz wrote: > Eric W. Biederman <ebiederm@...ssion.com> wrote: > > Or Gerlitz <or.gerlitz@...il.com> writes: > > >> To put things in place, DHCPv4 is supported with eIPoIB, the DHCP > >> UDP/IP payload isn't touched, only need to set the BOOTP broadcast > >> flag in the dhcp server config file. > > > Wrong. DHCPv4 is broken over eIPoIB. Coming from ethernet > > htype == 1 not 32 as required by RFC4390 > > hlen == 6 not 0 as required by RFC4390 > > The chaddr field is has 6 bytes of the ethernet mac address not the > > required 16 bytes of 0. The client-identifier field is optional over ethernet. > > An ethernet DHCPv4 client simply does not generate a dhcp packet that > > conforms to RFC4390. > > > > Therefore DHCPv4 over eIPoIB is broken, and a dhcp server or relay > > may reasonably look at the DHCP packet and drop it because it is garbage. > > > > You might find a forgiving dhcp server that doesn't drop insane packets > > on the floor and tries to make things work. > > Under the eIPoIB design, the VM DHCP interaction follows > Ethernet DHCP, and not the IPoIB DHCP (RFC 4390). > > The DHCP server has no reason to drop such packets. > > DHCP is a L7 (L5 to be precise) construct, I don't see > why that the fact IPoIB DHCP RFC exists, means/mandates > the DHCP server to care on the link layer type. > > Or. For example DHCP server could be configured with HW address/IP address table. -- MST -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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