Hi,
I've been experimenting with the nic_bridge a bit, and I came upon several problems/questions. First, when trying to connect a Linux VM through the bridge, it failed to obtain a IP from the DHCP server. I invistigated a little : the Discover packet get through, but the Offer is never transmitted to the client. The config shouldn't be the problem, considering the network worked fine with static IPs. I'm not sure if it is the origin of the issue, but the handling of the offer packet in nic.cc failed to parse the DHCP options (by adding debug prints in the option() function in dhcp.h, I saw that it got the first one right with the correct length 4, but then jumped 6 octet instead for the next option code).
I was also wondering if it would be possible to use several bridges in cascade. If I understand correctly, each Nic session opened on the bridge has an assigned mac address, but would it be feasible to use a single session for a sort of subnetwork?
Finally, the recent commits on master (between the 04-11 and the 04-25) have broken my vbox scenario : virtual box refuses to access
(sorry) a vdi virtual disk and reports a permission problem, but when I revert to the previous genode version, I have no problem. Is that a known issue or should Isend further informations?
Best regards, Charles
On Fri, May 13, 2016 at 6:19 PM, Charles HH <charleshh.genode@...9...> wrote:
Hi,
I've been experimenting with the nic_bridge a bit, and I came upon several problems/questions. First, when trying to connect a Linux VM through the bridge, it failed to obtain a IP from the DHCP server. I invistigated a little : the Discover packet get through, but the Offer is never transmitted to the client. The config shouldn't be the problem, considering the network worked fine with static IPs. I'm not sure if it is the origin of the issue, but the handling of the offer packet in nic.cc failed to parse the DHCP options (by adding debug prints in the option() function in dhcp.h, I saw that it got the first one right with the correct length 4, but then jumped 6 octet instead for the next option code).
I was also wondering if it would be possible to use several bridges in cascade. If I understand correctly, each Nic session opened on the bridge has an assigned mac address, but would it be feasible to use a single session for a sort of subnetwork?
Finally, the recent commits on master (between the 04-11 and the 04-25) have broken my vbox scenario : virtual box refuses to access
Hello Charles,
On 05/13/2016 06:19 PM, Charles HH wrote:
Hi,
I've been experimenting with the nic_bridge a bit, and I came upon several problems/questions. First, when trying to connect a Linux VM through the bridge, it failed to obtain a IP from the DHCP server. I invistigated a little : the Discover packet get through, but the Offer is never transmitted to the client. The config shouldn't be the problem, considering the network worked fine with static IPs. I'm not sure if it is the origin of the issue, but the handling of the offer packet in nic.cc failed to parse the DHCP options (by adding debug prints in the option() function in dhcp.h, I saw that it got the first one right with the correct length 4, but then jumped 6 octet instead for the next option code).
Parsing the DHCP responses and interpreting the option fields is done hardcoded within the nic_bridge. I would wonder if those field descriptions that are always used by it from dhcp.h should be wrong. As we use the nic_bridge permanently, and also used it in context of virtualization mechanisms provided by seoul and virtualbox, the hardcoded offsets should fail in our scenarios too.
However, its difficult for me to actually understand the possibly wrong behavior taken your description. Are you sure that the nic_bridge really processes DHCP offer packets, did you used e.g., wireshark to validate that the offer packet is actually received via your test-machine? Are you using some weird combination of virtualization techniques underneath your Genode setup, or is it running on bare hardware?
I was also wondering if it would be possible to use several bridges in cascade. If I understand correctly, each Nic session opened on the bridge has an assigned mac address, but would it be feasible to use a single session for a sort of subnetwork?
I would discourage you from using the nic_bridge in a cascade. Even if it works properly you do not win anything apart from performance degradation. The NIC bridge provides multiple sessions of the 'Nic' service while using a single 'Nic' session for forwarding requests. It implements a flavor of the Proxy-ARP protocol (RFC 1027). That means it allocates a virtual MAC address for each client. Whenever a client sends a packet, NIC bridge changes the sender's MAC address to the one it memorized for the client. Moreover, it monitors DHCP packets, and tracks the IP addresses assigned to each of its clients. Whenever ARP packets come from the outside, NIC bridge will answer them with the corresponding MAC address. Therefore, when you use cascade NIC bridges you do not cover the different clients, each client has a visible MAC address anyway that can be seen "on the wire". If you want to cover that multiple IP stacks are using the same MAC/IP you have to implement NAT, which is aimed according to our roadmap to be released soon. You can follow or participate in the discussion here:
Finally, the recent commits on master (between the 04-11 and the 04-25) have broken my vbox scenario : virtual box refuses to access
Sorry, I have no clue why this happening. Maybe somebody more into VirtualBox scenarios can help you.
Regards Stefan
Mobile security can be enabling, not merely restricting. Employees who bring their own devices (BYOD) to work are irked by the imposition of MDM restrictions. Mobile Device Manager Plus allows you to control only the apps on BYO-devices by containerizing them, leaving personal data untouched! https://ad.doubleclick.net/ddm/clk/304595813;131938128;j
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On 26.05.2016 13:12, Stefan Kalkowski wrote:
Finally, the recent commits on master (between the 04-11 and the 04-25) have broken my vbox scenario : virtual box refuses to access
Sorry, I have no clue why this happening. Maybe somebody more into VirtualBox scenarios can help you.
Please provide the last known good git commit of master and the one which seem to break your setup. Please provide also a branch with a run script showing this issue, so that we may try to reproduce it. Additionally we would need to know whether you run Genode as 32bit or 64bit host, virtualized or on native hardware, and which Guest OS you use.
Cheers,
Alex.
Hello Stefan,
Indeed, I'm quite doubtful that the dhcp offsets are really at cause. I had the following setup : Genode running on nova, booted directly from hard disk with grub. In Genode, virtualbox running a ubuntu 16.04 server VM, installed on a vdi accessed through rump_fs. I launched a dhclient on the VM, and monitored the network with wireshark from another computer (which also listened to the serial output). The dhclient never received any response, but I could see from wireshark that the DHCP server sent an offer with the correct IP. So I added several PDBG checks in the nic_bridge code and saw that the DHCP reply was processed in Nic::handle_ip, but the if(ext) condition was never entered. Naturally, I checked dhcp->option in net/dhcp.h to see why it didn't return a valid pointer, and, by adding debug messages (I included base/printf.h), I compared the options parsed with the ones from the packet (in wireshark) and noticed the incorrect "jump" (despite the first option's ext->length() being correct). I have no idea how to proceed from there...
I haven't had the time to check 16.05 and see if the issue is still relevant though...
Regards, Charles
On Thu, May 26, 2016 at 1:12 PM, Stefan Kalkowski < stefan.kalkowski@...1...> wrote:
Hello Charles,
On 05/13/2016 06:19 PM, Charles HH wrote:
Hi,
I've been experimenting with the nic_bridge a bit, and I came upon
several
problems/questions. First, when trying to connect a Linux VM through the bridge, it failed to obtain a IP from the DHCP server. I invistigated a little : the Discover packet get through, but the Offer is never transmitted to the client. The config shouldn't be the problem, considering the network worked fine with static IPs. I'm not sure if it is the origin of the issue, but the
handling
of the offer packet in nic.cc failed to parse the DHCP options (by adding debug prints in the option() function in dhcp.h, I saw that it got the first one right with the correct length 4, but then jumped 6 octet
instead
for the next option code).
Parsing the DHCP responses and interpreting the option fields is done hardcoded within the nic_bridge. I would wonder if those field descriptions that are always used by it from dhcp.h should be wrong. As we use the nic_bridge permanently, and also used it in context of virtualization mechanisms provided by seoul and virtualbox, the hardcoded offsets should fail in our scenarios too.
However, its difficult for me to actually understand the possibly wrong behavior taken your description. Are you sure that the nic_bridge really processes DHCP offer packets, did you used e.g., wireshark to validate that the offer packet is actually received via your test-machine? Are you using some weird combination of virtualization techniques underneath your Genode setup, or is it running on bare hardware?
I was also wondering if it would be possible to use several bridges in cascade. If I understand correctly, each Nic session opened on the bridge has an assigned mac address, but would it be feasible to use a single session for a sort of subnetwork?
I would discourage you from using the nic_bridge in a cascade. Even if it works properly you do not win anything apart from performance degradation. The NIC bridge provides multiple sessions of the 'Nic' service while using a single 'Nic' session for forwarding requests. It implements a flavor of the Proxy-ARP protocol (RFC 1027). That means it allocates a virtual MAC address for each client. Whenever a client sends a packet, NIC bridge changes the sender's MAC address to the one it memorized for the client. Moreover, it monitors DHCP packets, and tracks the IP addresses assigned to each of its clients. Whenever ARP packets come from the outside, NIC bridge will answer them with the corresponding MAC address. Therefore, when you use cascade NIC bridges you do not cover the different clients, each client has a visible MAC address anyway that can be seen "on the wire". If you want to cover that multiple IP stacks are using the same MAC/IP you have to implement NAT, which is aimed according to our roadmap to be released soon. You can follow or participate in the discussion here:
Finally, the recent commits on master (between the 04-11 and the 04-25) have broken my vbox scenario : virtual box refuses to access
Sorry, I have no clue why this happening. Maybe somebody more into VirtualBox scenarios can help you.
Regards Stefan
Mobile security can be enabling, not merely restricting. Employees who bring their own devices (BYOD) to work are irked by the imposition of MDM restrictions. Mobile Device Manager Plus allows you to control only the apps on BYO-devices by containerizing them, leaving personal data
untouched!
https://ad.doubleclick.net/ddm/clk/304595813;131938128;j
genode-main mailing list genode-main@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/genode-main
-- Stefan Kalkowski Genode Labs
http://www.genode-labs.com/ · http://genode.org/
Mobile security can be enabling, not merely restricting. Employees who bring their own devices (BYOD) to work are irked by the imposition of MDM restrictions. Mobile Device Manager Plus allows you to control only the apps on BYO-devices by containerizing them, leaving personal data untouched! https://ad.doubleclick.net/ddm/clk/304595813;131938128;j _______________________________________________ genode-main mailing list genode-main@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/genode-main
Hi Charles,
On 06/01/2016 06:03 PM, Charles HH wrote:
Hello Stefan,
Indeed, I'm quite doubtful that the dhcp offsets are really at cause. I had the following setup : Genode running on nova, booted directly from hard disk with grub. In Genode, virtualbox running a ubuntu 16.04 server VM, installed on a vdi accessed through rump_fs. I launched a dhclient on the VM, and monitored the network with wireshark from another computer (which also listened to the serial output). The dhclient never received any response, but I could see from wireshark that the DHCP server sent an offer with the correct IP. So I added several PDBG checks in the nic_bridge code and saw that the DHCP reply was processed in Nic::handle_ip, but the if(ext) condition was never entered. Naturally, I checked dhcp->option in net/dhcp.h to see why it didn't return a valid pointer, and, by adding debug messages (I included base/printf.h), I compared the options parsed with the ones from the packet (in wireshark) and noticed the incorrect "jump" (despite the first option's ext->length() being correct). I have no idea how to proceed from there...
its hard to follow without knowing the exact options etc. Can you please provide your changes (printf) in form of a diff/patch, and in addition the log output, and tell me exactly what header is wroing by means of the output?
I haven't had the time to check 16.05 and see if the issue is still relevant though...
It might be an option, but actually the nic_bridge did not changed recently.
Regards Stefan
Regards, Charles
On Thu, May 26, 2016 at 1:12 PM, Stefan Kalkowski < stefan.kalkowski@...1...> wrote:
Hello Charles,
On 05/13/2016 06:19 PM, Charles HH wrote:
Hi,
I've been experimenting with the nic_bridge a bit, and I came upon
several
problems/questions. First, when trying to connect a Linux VM through the bridge, it failed to obtain a IP from the DHCP server. I invistigated a little : the Discover packet get through, but the Offer is never transmitted to the client. The config shouldn't be the problem, considering the network worked fine with static IPs. I'm not sure if it is the origin of the issue, but the
handling
of the offer packet in nic.cc failed to parse the DHCP options (by adding debug prints in the option() function in dhcp.h, I saw that it got the first one right with the correct length 4, but then jumped 6 octet
instead
for the next option code).
Parsing the DHCP responses and interpreting the option fields is done hardcoded within the nic_bridge. I would wonder if those field descriptions that are always used by it from dhcp.h should be wrong. As we use the nic_bridge permanently, and also used it in context of virtualization mechanisms provided by seoul and virtualbox, the hardcoded offsets should fail in our scenarios too.
However, its difficult for me to actually understand the possibly wrong behavior taken your description. Are you sure that the nic_bridge really processes DHCP offer packets, did you used e.g., wireshark to validate that the offer packet is actually received via your test-machine? Are you using some weird combination of virtualization techniques underneath your Genode setup, or is it running on bare hardware?
I was also wondering if it would be possible to use several bridges in cascade. If I understand correctly, each Nic session opened on the bridge has an assigned mac address, but would it be feasible to use a single session for a sort of subnetwork?
I would discourage you from using the nic_bridge in a cascade. Even if it works properly you do not win anything apart from performance degradation. The NIC bridge provides multiple sessions of the 'Nic' service while using a single 'Nic' session for forwarding requests. It implements a flavor of the Proxy-ARP protocol (RFC 1027). That means it allocates a virtual MAC address for each client. Whenever a client sends a packet, NIC bridge changes the sender's MAC address to the one it memorized for the client. Moreover, it monitors DHCP packets, and tracks the IP addresses assigned to each of its clients. Whenever ARP packets come from the outside, NIC bridge will answer them with the corresponding MAC address. Therefore, when you use cascade NIC bridges you do not cover the different clients, each client has a visible MAC address anyway that can be seen "on the wire". If you want to cover that multiple IP stacks are using the same MAC/IP you have to implement NAT, which is aimed according to our roadmap to be released soon. You can follow or participate in the discussion here:
Finally, the recent commits on master (between the 04-11 and the 04-25) have broken my vbox scenario : virtual box refuses to access
Sorry, I have no clue why this happening. Maybe somebody more into VirtualBox scenarios can help you.
Regards Stefan
Mobile security can be enabling, not merely restricting. Employees who bring their own devices (BYOD) to work are irked by the imposition of MDM restrictions. Mobile Device Manager Plus allows you to control only the apps on BYO-devices by containerizing them, leaving personal data
untouched!
https://ad.doubleclick.net/ddm/clk/304595813;131938128;j
genode-main mailing list genode-main@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/genode-main
-- Stefan Kalkowski Genode Labs
http://www.genode-labs.com/ · http://genode.org/
Mobile security can be enabling, not merely restricting. Employees who bring their own devices (BYOD) to work are irked by the imposition of MDM restrictions. Mobile Device Manager Plus allows you to control only the apps on BYO-devices by containerizing them, leaving personal data untouched! https://ad.doubleclick.net/ddm/clk/304595813;131938128;j _______________________________________________ genode-main mailing list genode-main@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/genode-main
What NetFlow Analyzer can do for you? Monitors network bandwidth and traffic patterns at an interface-level. Reveals which users, apps, and protocols are consuming the most bandwidth. Provides multi-vendor support for NetFlow, J-Flow, sFlow and other flows. Make informed decisions using capacity planning reports. https://ad.doubleclick.net/ddm/clk/305295220;132659582;e
genode-main mailing list genode-main@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/genode-main
Hi Stefan,
Sorry for the delay. The following diff should be enough to explain the issue :
diff --git a/repos/os/include/net/dhcp.h b/repos/os/include/net/dhcp.h index da492d0..ea8e712 100644 --- a/repos/os/include/net/dhcp.h +++ b/repos/os/include/net/dhcp.h @@ -22,6 +22,7 @@ #include <net/ethernet.h> #include <net/ipv4.h> #include <net/udp.h> +#include <base/printf.h>
namespace Net { class Dhcp_packet; }
@@ -215,6 +216,7 @@ class Net::Dhcp_packet void *ptr = &_opts; while (true) { Option *ext = new (ptr) Option(); + PLOG("DHCP Option : %d %d", (int)ext->code(), (int)ext->length()); if (ext->code() == op) return ext; if (ext->code() == END || ext->code() == 0) diff --git a/repos/os/src/server/nic_bridge/nic.cc b/repos/os/src/server/nic_bridge/nic.cc index 949f5a1..389d4ce 100644 --- a/repos/os/src/server/nic_bridge/nic.cc +++ b/repos/os/src/server/nic_bridge/nic.cc @@ -79,11 +79,15 @@ bool Net::Nic::handle_ip(Ethernet_frame *eth, Genode::size_t size) { if (Dhcp_packet::is_dhcp(udp)) { Dhcp_packet *dhcp = new (udp->data()) Dhcp_packet(size - sizeof(Ipv4_packet) - sizeof(Udp_packet)); + PLOG("DHCP Packet received");
/* check for DHCP ACKs containing new client ips */ if (dhcp->op() == Dhcp_packet::REPLY) { + PLOG("DHCP reply"); Dhcp_packet::Option *ext = dhcp->option(Dhcp_packet::MSG_TYPE); + PLOG("Got MSG_TYPE option"); if (ext) { + PLOG("if(ext) succeeded"); /* * extract the IP address and set it in the * client's session-component @@ -97,7 +101,7 @@ bool Net::Nic::handle_ip(Ethernet_frame *eth, Genode::size_t size) { if (node)
node->component()->set_ipv4_address(dhcp->yiaddr()); } - } + } else PLOG("if(ext) failed"); } } }
With these modifications, I get the following debug output when a DHCP Offer is received (following a request from the VM) :
[init -> nic_bridge] DHCP Packet received [init -> nic_bridge] DHCP reply [init -> nic_bridge] DHCP Option : 1 4 [init -> nic_bridge] DHCP Option : 172 16 [init -> nic_bridge] DHCP Option : 111 114 [init -> nic_bridge] DHCP Option : 0 0 [init -> nic_bridge] Got MSG_TYPE option [init -> nic_bridge] if(ext) failed
While the options in the actual packet (as seen in wireshark) should be :
Option: (1) Subnet Mask Length: 4 Subnet Mask: 255.255.0.0 (255.255.0.0) Option: (3) Router Length: 4 Router: 172.16.254.254 (172.16.254.254) Option: (6) Domain Name Server Length: 4 Domain Name Server: 172.16.254.253 (172.16.254.253) Option: (12) Host Name Length: 23 Host Name: ####################### Option: (15) Domain Name Length: 11 Domain Name: ########### Option: (42) Network Time Protocol Servers Length: 4 Network Time Protocol Server: 172.16.254.254 (172.16.254.254) Option: (51) IP Address Lease Time Length: 4 IP Address Lease Time: (600s) 10 minutes Option: (53) DHCP Message Type Length: 1 DHCP: Offer (2) Option: (54) DHCP Server Identifier Length: 4 DHCP Server Identifier: 172.24.100.53 (172.24.100.53) Option: (58) Renewal Time Value Length: 4 Renewal Time Value: (300s) 5 minutes Option: (59) Rebinding Time Value Length: 4 Rebinding Time Value: (1800s) 30 minutes Option: (255) End Option End: 255
0110 01 04 ff ff 00 00 0120 03 04 ac 10 fe fe 06 04 ac 10 fe fd 0c 17 ## ## 0130 ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## 0140 ## ## ## ## ## 0f ## ## ## ## ## ## ## ## ## ## 0150 ## ## 2a 04 ac 10 fe fe 33 04 00 00 02 58 35 01 0160 02 36 04 ac 18 64 35 3a 04 00 00 01 2c 3b 04 00 0170 00 07 08 ff
So the first jump from option 1 to option 3 actually landed two bytes off (or elsewhere entirely but that seems unlikely). I guess the next step should be to check the memory addresses of the bytes to see why this happened... The bridge isn't really critical to my setup though anyway.
Regards, Charles
On Fri, Jun 3, 2016 at 8:05 AM, Stefan Kalkowski < stefan.kalkowski@...1...> wrote:
Hi Charles,
On 06/01/2016 06:03 PM, Charles HH wrote:
Hello Stefan,
Indeed, I'm quite doubtful that the dhcp offsets are really at cause. I
had
the following setup : Genode running on nova, booted directly from hard disk with grub. In Genode, virtualbox running a ubuntu 16.04 server VM, installed on a vdi accessed through rump_fs. I launched a dhclient on the VM, and monitored the network with wireshark from another computer (which also listened to the serial output). The dhclient never received any response, but I could see from wireshark that the DHCP server sent an offer with the correct IP. So I added several PDBG checks in the nic_bridge code and saw that the
DHCP
reply was processed in Nic::handle_ip, but the if(ext) condition was
never
entered. Naturally, I checked dhcp->option in net/dhcp.h to see why it didn't
return
a valid pointer, and, by adding debug messages (I included
base/printf.h),
I compared the options parsed with the ones from the packet (in
wireshark)
and noticed the incorrect "jump" (despite the first option's
ext->length()
being correct). I have no idea how to proceed from there...
its hard to follow without knowing the exact options etc. Can you please provide your changes (printf) in form of a diff/patch, and in addition the log output, and tell me exactly what header is wroing by means of the output?
I haven't had the time to check 16.05 and see if the issue is still relevant though...
It might be an option, but actually the nic_bridge did not changed recently.
Regards Stefan
Hello Charles,
I think there is an issue in the calculation of the pointer to the next DHCP option. Could you please try the attached patch?
Greets
Hi Christian,
The patch worked. The options are now parsed correctly. I still have a problem with the DHCP server sending the Offer to the VM mac address (taken from the DHCP options I would assume) instead of to the bridge. I think that's quite an unusual behavior for a DHCP server though, so I don't think it deserves particular attention...
Thank you for your time, Charles
On Tue, Jun 14, 2016 at 4:25 PM, Christian Helmuth < christian.helmuth@...1...> wrote:
Hello Charles,
I think there is an issue in the calculation of the pointer to the next DHCP option. Could you please try the attached patch?
Greets
Christian Helmuth Genode Labs
http://www.genode-labs.com/ · http://genode.org/ https://twitter.com/GenodeLabs · /ˈdʒiː.nəʊd/
Genode Labs GmbH · Amtsgericht Dresden · HRB 28424 · Sitz Dresden Geschäftsführer: Dr.-Ing. Norman Feske, Christian Helmuth
What NetFlow Analyzer can do for you? Monitors network bandwidth and traffic patterns at an interface-level. Reveals which users, apps, and protocols are consuming the most bandwidth. Provides multi-vendor support for NetFlow, J-Flow, sFlow and other flows. Make informed decisions using capacity planning reports. https://ad.doubleclick.net/ddm/clk/305295220;132659582;e _______________________________________________ genode-main mailing list genode-main@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/genode-main
Hello Charles,
On Wed, Jun 15, 2016 at 11:22:01AM +0200, Charles HH wrote:
The patch worked. The options are now parsed correctly.
Great.
I still have a problem with the DHCP server sending the Offer to the VM mac address (taken from the DHCP options I would assume) instead of to the bridge. I think that's quite an unusual behavior for a DHCP server though, so I don't think it deserves particular attention...
This may result from the simplicity of our current bridge implementation. It may be better to implement DHCP relaying
https://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol#DHCP_relay...
to force the DHCP server to send an unicast reply to the bridge MAC address. Also, it may be the case that our implementation misses one picky detail when constructing the DHCP request packet.
Regards
Thanks to Charles for reporting! And thanks to Christian for investigating the root cause!
This is the second bug in the net/*.h files of the nic_bridge and it indicates that we have to review these old rotten piece of network headers. Mea culpa!
Regards Stefan
On 06/15/2016 12:30 PM, Christian Helmuth wrote:
Hello Charles,
On Wed, Jun 15, 2016 at 11:22:01AM +0200, Charles HH wrote:
The patch worked. The options are now parsed correctly.
Great.
I still have a problem with the DHCP server sending the Offer to the VM mac address (taken from the DHCP options I would assume) instead of to the bridge. I think that's quite an unusual behavior for a DHCP server though, so I don't think it deserves particular attention...
This may result from the simplicity of our current bridge implementation. It may be better to implement DHCP relaying
https://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol#DHCP_relay...
to force the DHCP server to send an unicast reply to the bridge MAC address. Also, it may be the case that our implementation misses one picky detail when constructing the DHCP request packet.
Regards
-
Alexander Boettcher -
Charles HH -
Christian Helmuth -
Stefan Kalkowski