On Thu, Jul 23, 2015 at 10:13:20AM +0000, Fu, Siyuan wrote: > Michael, > > It's not because any benefit, it's because there is actually no place to put > the static local variable. The IaDescriptor.IaId is defined in UEFI spec, so > Dhcp6->Configure() function could only use caller provided IaId number and > can't modify it. And we couldn't use static local variable in NetLib, because > the library is statically linked to IP6 and PXE driver, so there are actually > 2 static variable in these 2 driver. >
Thank you for the explaination, now I understood why. If you have any patch for this and need testing, please let me know and I'm glad to help. Thanks, Michael > Best Regards > Siyuan > > -----Original Message----- > From: Michael Chang [mailto:mch...@suse.com] > Sent: Thursday, July 23, 2015 5:43 PM > To: Fu, Siyuan > Cc: edk2-devel@lists.sourceforge.net; Ye, Ting > Subject: Re: [edk2] DHCPv6 IAID and NetRandomInitSeed problem in OVMF > > On Thu, Jul 23, 2015 at 09:01:38AM +0000, Fu, Siyuan wrote: > > Hi, Michael > > > > It's indeed a problem that NET_RANDOM (NetRandomInitSeed ()) may return > > same value if the time service is not accuracy enough on some platform. And > > as you said it's used to give unique but not necessarily to be real random > > number, so I think we could just add some salt into the seed. I think the > > platform monotonic counter may be a good choose, we can call > > gBS->GetNextMonotonicCount() and add the low 32 bits of MC to the seed. > > This could make the returned seed unique even GetTime() return all zero in > > the worst case. What do you think about it? > > It sounds good for me. But I'd like to know what is the benefit compared to > increment by static local variable? > > > > > For your recommendation #3, the IaId is configured by Ip6Dxe and PXE > > driver, and there are no interface to exchange the index between them. > > DHCP6 driver just use the IaId configured by caller and it couldn't modify > > it. And for 4, one of the design intention of PXE boot is "platform doesn't > > need any pre-configuration", so it's also not acceptable. > > Actually I'm not sure about the need to create automatic policy. Is there any > function or feature in UEFI preboot environment depend on it to work > correctly (likely it is for booting iSCSI disks, but that can be done in > other settings) ? > > Thanks, > Michael > > > > > Best Regards, > > Siyuan > > > > -----Original Message----- > > From: Michael Chang [mailto:mch...@suse.com] > > Sent: Thursday, July 23, 2015 3:33 PM > > To: edk2-devel@lists.sourceforge.net > > Subject: [edk2] DHCPv6 IAID and NetRandomInitSeed problem in OVMF > > > > Hi, > > > > I have problem in IPv6 PXE booting under OVMF that the process terminated > > immediately right after selecting the UEFI IPv6 boot entry. I have to > > change the IPv6 config policy from automatic to manual to get things > > working again for me. > > > > I looked a bit into this problem, it was terminated by the error in > > IaId check > > > > in NetworkPkg/Dhcp6Dxe/Dhcp6Impl.c::EfiDhcp6Configure function > > > > // > > // Make sure the (IaId, IaType) is unique over all the instances. > > // > > NET_LIST_FOR_EACH (Entry, &Service->Child) { > > Other = NET_LIST_USER_STRUCT (Entry, DHCP6_INSTANCE, Link); > > if (Other->IaCb.Ia != NULL && > > Other->IaCb.Ia->Descriptor.Type == > > Dhcp6CfgData->IaDescriptor.Type && > > Other->IaCb.Ia->Descriptor.IaId == Dhcp6CfgData->IaDescriptor.IaId > > ) { > > return EFI_INVALID_PARAMETER; > > } > > } > > > > Which would be saying clearly it was not "unique" among all the > > running > > DHCPv6 instances. At that time there should be only two: > > > > 1. The IPv6 config instance, while the policy is set to automatic > > would exchange information with server with the IaId initialized at > > > > NetworkPkg/Ip6Dxe/Ip6ConfigImpl.c::Ip6ConfigInitInstance > > > > Instance->IaId = NET_RANDOM (NetRandomInitSeed ()); > > > > for (Index = 0; Index < IpSb->SnpMode.HwAddressSize; Index++) { > > Instance->IaId |= (IpSb->SnpMode.CurrentAddress.Addr[Index] << > > ((Index << 3) & 31)); > > } > > > > 2. The IPv6 PXE Base code driver would start another DHCPv6 session > > with the IaId initialized at > > > > NetworkPkg/UefiPxeBcDxe/PxeBcDriver.c::PxeBcCreateIp6Children > > > > // > > // Generate a random IAID for the Dhcp6 assigned address. > > // > > Private->IaId = NET_RANDOM (NetRandomInitSeed ()); > > if (Private->Snp != NULL) { > > for (Index = 0; Index < Private->Snp->Mode->HwAddressSize; Index++) { > > Private->IaId |= (Private->Snp->Mode->CurrentAddress.Addr[Index] << > > ((Index << 3) & 31)); > > } > > } > > > > Unfortunately both IaId collides, and quite surprisingly it's NET_RANDOM > > (NetRandomInitSeed ()), or NetRandomInitSeed () generates the same number > > for them. > > > > UINT32 > > EFIAPI > > NetRandomInitSeed ( > > VOID > > ) > > { > > EFI_TIME Time; > > UINT32 Seed; > > > > gRT->GetTime (&Time, NULL); > > Seed = (~Time.Hour << 24 | Time.Day << 16 | Time.Minute << 8 | > > Time.Second); > > Seed ^= Time.Nanosecond; > > Seed ^= Time.Year << 7; > > > > return Seed; > > } > > > > The returned Time.Nanosecond is always zero as the timer resolution is l Hz > > for PC-AT CMOS RTC, that seems to be default real time clock driver used by > > OVMF. At least from .dsc file it says so .. > > > > > > PcAtChipsetPkg/PcatRealTimeClockRuntimeDxe/PcatRealTimeClockRuntimeDxe > > .inf > > > > The NetRandomInitSeed is not random enough in this case, and the > > NET_RANDOM marco is even more confusing as it's not a random number > > generator either (so what is good for always feeding random "seed" to > > a deterministic mathematic fucntion ??) > > > > I don't have good idea how to fix the problem, but here are of my thoughs. > > > > 1. Use real timer clock driver which could provide higher resolution for > > time service. Qemu is able to provide HPET timer but I don't know how to > > configure OVMF to use it. > > > > 2. Use GetPerformanceCounter(), but that would increase image size by > > linking TimerLib. > > > > 3. The IaId has to be "unique" thus not necessarily to be random, probably > > it should be derived by some properties like MAC address and an assgined > > index (staring from zero) for the interface to be confiured. > > > > 4. Use manual as default IPv6 policy, but that just hide the problem. > > > > Hope that my information and findings helps. :) > > > > Thanks, > > Michael > > > > ---------------------------------------------------------------------- > > -------- _______________________________________________ > > edk2-devel mailing list > > edk2-devel@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/edk2-devel ------------------------------------------------------------------------------ _______________________________________________ edk2-devel mailing list edk2-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/edk2-devel
