Grant Taylor wrote in &lt;1dbc110c-8844-040d-a08d-07914094b47f(a)spamtrap.tnetconsulting.net&gt;: |On 9/21/20 3:38 PM, Steffen Nurpmeso wrote: |> Bridges usually do not work with wireless interfaces, it need some |> v?eth. | |Is it the bridge that's the problem or is it the wireless interface |that's the problem? | |My understanding is that some (many?) wireless interfaces are funky |regarding multiple MAC addresses. Mostly in that they don't work with |extra MAC addresses. My understanding also is about MAC changing, but it seems there are drivers which can do something about it. Not my area, sorry. |What would you do with veth interfaces in this context? This is exactly the nice thing about the approach i use, the one side of the veth pair that is not in the namespace simply plugs into whatever network environment there is on the host, as long as the host as a route to it. The other end, jailed in the namespace, can regulary be used by a bridge device. And is constant and self-sufficient. I use fixed addresses, for example. (Parsed from a hosts.txt that is also read in by dnsmasq(8) so that the host and the VMs find each other. All i have to adjust is the hosts.txt. Having said that, i can improve this by deriving the MAC address from that file, too.) |> And those br* tools are not everywhere, too (grr). | |I've been able to use ip to do much of what I used to do with brctl. | | ip link add bri0 type bridge | ip link set eth1 master bri0 | |(from memory) Yes. It is just that when you search the internet for Linux and bridges you will find mostly brctl or systemd things. (Generally spoken the amount of let me say whisked crap is near hundred percent in fact.) |> Have you ever considered network namespaces? | |What would network namespaces provide in this context? | |Would you run the $EMULATOR in the network namespace (~container)? Yes. |What does that get you that running the $EMULATOR in the main / root / |unnamed network namespace does not get you? -- If anything, I'd think |that running the $EMULATOR in the network namespace would add additional |networking complexity. You have seen all the configuration there is. It is isolated, it is not affected by the firewall rules of the host, the firewall rules of the host do not take care of this thing at all, attack surface is thus only kernel bugs, i thing, and anything on the inside can be hardwired. No worries. |Don't get me wrong, I'm all for network namespaces and doing fun(ky) |things with them. I've emulated entire corporate networks with network |namespaces. I've currently got nine of them on the system I'm replying |from, with dynamic routing. No worries. |> After over a year of using proxy_arp based pseudo bridging (cool!) | |I'll argue that Proxy ARP /is/ a form of routing. ;-) Your system |replies to ARP requests for the IP(s) behind it and the packets are sent |to it as if it's a router. }:-) Yes it is cool. The "Linux Advanced Routing & Traffic Control HOWTO" (twenty years ago such great things were written and said "Welcome, gentle reader", unfortunately that all stopped when the billions came over Linux i think, but, of course, today the manual pages are great) says /proc/sys/net/ipv4/conf/DEV/proxy_arp If you set this to 1, this interface will respond to ARP requests for addresses the kernel has routes to. Can be very useful when building 'ip pseudo bridges'. Do take care that your netmasks are very correct before enabling this! Also be aware that the rp_filter, mentioned elsewhere, also operates on ARP queries. |> i finally wrapped my head around veth, | |I find veth to be quite helpful. {MAC,IP}{VLAN,VTAP} are also fun. | |Aside: {MAC,IP}{VLAN,VTAP} is slightly more difficult to get working. |In my experience, {MAC,IP}{VLAN,VTAP} don't support talking to the host |directly, instead you need to create an additional {MAC,IP}{VLAN,VTAP} |and have the hose use it as if it is it's own guest. | |> with it and Linux network namespaces i loose 40 percent ping response |> speed, but have a drastically reduced need for configuration. | |I've never noticed any sort of increased latency worth mentioning. Compared to proxy_arp it was 40 percent here. However, this was with kernel 4.19 and the network driver (R8822BE) was in staging, now with 5.8 it is not (RTW88) but terribly broken or buggy or whatever. It must be said this driver seems to be very complicated, the R8822BE had a megabyte of code infrastructure iirc. But it is terrible, and now i know that audio via bluetooth and wlan throughput are highly dependent. (Or can.) |> What i have is this, maybe you find it useful. It does not need |> any firewall rules. (Except allowing 10.0.0.0/8.) |> |> In my net-qos.sh (which is my shared-everywhere firewall and tc |> script) |> |> vm_ns_start() { |> #net.ipv4.conf.all.arp_ignore=0 |> sysctl -w \ |> net.ipv4.ip_forward=1 |> |> ${ip} link add v_n type veth peer name v_i |> ${ip} netns add v_ns |> ${ip} link set v_i netns v_ns | |If you create the netns first, then you can have the veth interface |created and moved into the network namespace in one command. | | ${ip} link add v_n type veth peer name v_i netns v_ns | |Note: This does create the v_i veth interface in the network namespace |that you're running the command in and then automatically move it for you. I did not know that, will try it out. |> ${ip} a add 10.0.0.1/8 dev v_n |> ${ip} link set v_n up |> ${ip} route add 10.0.0.1 dev v_n | |Why are you adding a (host) route to 10.0.0.1 when it's part of |10.0.0.0/8 which is going out the same interface? I assign an address to the interface, and make that interface routable from the host. |> ${ip} netns exec v_ns ${ip} link set lo up |> #if [ -z "$BR" ]; then |> # ${ip} netns exec v_ns ip addr add 10.1.0.1/8 dev v_i broadcast \ |> + |> # ${ip} netns exec v_ns ip link set v_i up |> # ${ip} netns exec v_ns ip route add default via 10.0.0.1 |> #else |> ${ip} netns exec v_ns ${ip} link set v_i up |> ${ip} netns exec v_ns ${ip} link add v_br type bridge | |Why are you adding a bridge inside the v_ns network namespace? This is where all the VMs plug into. |> ${ip} netns exec v_ns ${ip} addr add 10.1.0.1/8 dev v_br \ |> broadcast + |> ${ip} netns exec v_ns ${ip} link set v_br up |> ${ip} netns exec v_ns ${ip} link set v_i master v_br | |Why are you adding the v_i interface to the bridge /inside/ the network |namespace? That is the other side of the veth interface pair of course. |> ${ip} netns exec v_ns ${ip} route add default via 10.0.0.1 |> #fi |>} | |What does creating a bridge with a single interface /inside/ of the |network namespace get you? | |I would have assumed that you were creating the bridge outside the |network namespace and adding the network namespace's outside veth to |said bridge. No. The purpose is to be able to create a network of any number of VMs somewhere, so those go via the bridge, no? This network is self-sufficient ANY HOST HOWEVER ONLINE <---> VETH -|- VETH IN NAMESPACE ^ | ANY NUMBER OF VMS <-> BRIDGE < |> vm_ns_stop() { |> ${ip} netns del v_ns |> |> ^ That easy it is! | |Yep. I've done a LOT of things like that. Though I have the bridge |outside. Why would you want to do this? I do not understand. |> #net.ipv4.conf.all.arp_ignore=1 | |What was (historically, since it's commented out) the purpose for |setting arp_ignore to 1. Yeah, this is a leftover from the proxy_arp based pseudo-bridge. Not to forget it, maybe. I should have removed it before posting. I am not a network expert ok, especially not so Linux-specific. |> sysctl -w \ |> net.ipv4.ip_forward=0 |>} |> |> And then, in my /x/vm directory the qemu .ifup.sh script |> |> #!/bin/sh - |> |> if [ "$VMNETMODE" = bridge ]; then |> ip link set dev $1 master v_br | |This is more what I would expect. This is just the startup of a VM, it registers at the bridge. |> ip link set $1 up |> elif [ "$VMNETMODE" = proxy_arp ]; then |> echo 1 > /proc/sys/net/ipv4/conf/$1/proxy_arp |> ip link set $1 up |> ip route add $VMADDR dev $1 | |I guess the route is because you're using Proxy ARP. I am _not_ using proxy_arp no more. This is a leftover, at the beginning i made it configurable and could switch in between the different approaches via a setting in /x/vm/.run.sh. I should have removed it before posting. |That makes me ask, is the 10.0.0.0/8 network also used on the outside |home LAN? That one is isolated, i can reach it from the host, and they can talk to the host, each other and the internet. I never placed servers addressable from the outside in such a thing, this is only a laptop without fixed address. I guess in order to allow a public accessible server to live in the namespace i would maybe need an ipfilter rule on the host. |> else |> echo >&2 Unknown VMNETMODE=$VMNETMODE |> fi | |;-) | |> Of course qemu creates the actual device for me here. |> The .ifdown.sh script i omit, it is not used in this "vbridge" |> mode. It would do nothing really, and it cannot be called because |> i now can chroot into /x/vm (needs dev/u?random due to libcrypt |> needing it though it would not need them, but i cannot help it). | |You can bind mount /dev into the chroot. That way you could chroot in. |Much like Gentoo does during installation. Yes --bind mounting is cool also. But i definetely do not want to give the VM an entire /dev, it only needs u?random and that _only_ because libcrypt (linked into qemu) needs it, even though it is not actually used (the Linux getrandom system call is used instead). |> This then gets driven by a .run.sh script (which is called by the |> real per-VM scripts, like |> |> #!/bin/sh - |> # root.alp-2020, steffen: Sway |> |> debug= |> vmsys=x86_64 |> vmname=alp-2020 |> vmimg=.alp-2020-amd64.vmdk |> vmpower=half |> vmmac=52:54:45:01:00:12 |> vmcustom= #'-boot menu=on -cdrom /x/iso/alpine-virt-3.12.0-x86_64.iso' |> |> . /x/vm/.run.sh |> # s-sh-mode |> |> so, and finally invokes qemu like so |> |> echo 'Monitor at '$0' monitor' |> eval exec $sudo /bin/ip netns exec v_ns /usr/bin/qemu-system-$vmsys \ |> -name $VMNAME $runas $chroot \ |> $host $accel $vmdisp $net $usb $vmrng $vmcustom \ |> -monitor telnet:127.0.0.1:$monport,server,nowait \ |> -drive file=$vmimg,index=0,if=ide$drivecache \ |> $redir |> |> Users in the vm group may use that sudo, qemu is executed in the |> v_ns network namespace under runas='-runas vm' and jailed via |> chroot='-chroot .'. It surely could be more sophisticated, more |> cgroups, whatever. Good enough for me. | |:-) | |Have you spent any time looking at unshare and / or nsenter? | | # Spawn the lab# NetNSs and set it's hostname. | unshare --mount=/run/mountns/${1} --net=/run/netns/${1} |--uts=/run/utsns/${1} /bin/hostname ${1} | # Bring up the loopback interface. | nsenter --mount=/run/mountns/${1} --net=/run/netns/${1} |--uts=/run/utsns/${1} /bin/ip link set dev lo up | |I use the mount, net, and uts namespaces. RTFM for more details on |different combinations of namespaces. Yes. But no, i do not really need it, i use it only for qemu instances. Interesting would be imposing hard CPU and memory restrictions, especially if i would use this approach for creating servers, too. This is a future task, however. |> That .run.sh does enter |> |> if [ "$1" = monitor ]; then |> echo 'Entering monitor of '$VMNAME' ('$VMADDR') at '$monport |> eval exec $sudo /bin/ip netns exec v_ns telnet localhost $monport |> exit 5 |> |> and enters via ssh |> |> elif [ "$1" = ssh ]; then |> echo 'SSH into '$VMNAME' ('$VMADDR')' |> doex=exec |> if command -v tmux >/dev/null 2>&1 && [ -n "$TMUX_PANE" ]; then |> tmux set window-active-style bg=colour231,fg=colour0 |> doex= |> fi |> ( eval $doex ssh $VMADDR ) |> exec tmux set window-active-style bg=default,fg=default |> exit 5 |> |> for me. (I use VMs in Donald Knuth emacs colour scheme it seems, |> at least more or less. VMs here, VM there. Hm.) | |... VM everywhere. | |But ... are they /really/ VMs? | |You're running an /emulator/* in a (home grown) /container/. | |}:-) | |*Okay. QEMU can be more of a VM than an emulator, depending on command |line options. | |> Overall this network namespace thing is pretty cool. Especially |> since, compared to FreeBSD jails, for example, you simply can run |> a single command. Unfair comparison though. WHat i'd really |> wish would be a system which is totally embedded in that |> namespace/jail idea. I.e., _one_ /, and then only moving targets |> mounted via overlayfs into "per-jail" directories. Never found |> time nor motivation to truly try this out. | |I'm not that familiar with jails. But I'm convinced that there are some |possibilities with namespaces (containers) that may come close. | |Network namespaces (ip netns ...) don't alter the mount namespace. |That's one of the advantages of unshare / nsenter. You can create new |namespace (container) specific mount configurations. Yeah like i said, i could impose more restrictions on programs running inside that namespace, qemu also shows some security flaws at times, but this is really just for testing purposes etc. --steffen | |Der Kragenbaer, The moon bear, |der holt sich munter he cheerfully and one by one |einen nach dem anderen runter wa.ks himself off |(By Robert Gernhardt)

Hello. Grant Taylor wrote in &lt;0f0083d2-1fc6-87dd-3001-6fa7e3752c79(a)tnetconsulting.net&gt;: |On 9/22/20 8:54 AM, Steffen Nurpmeso wrote: |> My understanding also is about MAC changing, but it seems there are |> drivers which can do something about it. Not my area, sorry. | |That matches my understanding. And that is fuzzy on my side, the best i have heard was on some FreeBSD not too long ago, where the same problem exists. ..Yes. This is exactly the message i remembered: https://marc.info/?l=freebsd-current&m=155924713003353&w=2 (The relevant part is ) Not much. |> This is exactly the nice thing about the approach i use, the one |> side of the veth pair that is not in the namespace simply plugs into |> whatever network environment there is on the host, as long as the |> host as a route to it. | |Sorry, I was asking for more clarification on what you do with the host |end of the veth to connect it to the rest of your environment. Nothing. I only set the route. |> The other end, jailed in the namespace, can regulary be used by a |> bridge device. | |Yes. | |I'm wondering why you are attaching the NetNS end of the veth to a |bridge instead of just using the veth directly. Ha. That could very well be because i was desperately trying to create a bridge all the time, but it just was not working at all. So i turned to proxy_arp "pseudo-bridging", with just having routes and the TAP devices for the VMs, nothing more. A wild chaos universe thus. You know, to me this is just a programmatic problem, i just do not understand. Why does it matter whether you have eth0 or wlp1s0? I can go into the internet with both, why can i create a bridge on one but not the other? That does not make sense. Just do it? It works when i inject a VETH pair, so may it be like this. Having the bridge now makes things easy, i just make it the master of anything which is plugged into it. Yes, so easy are things if you never programmed a network hardware driver! |> And is constant and self-sufficient. I use fixed addresses, for |> example. (Parsed from a hosts.txt that is also read in by dnsmasq(8) |> so that the host and the VMs find each other. All i have to adjust |> is the hosts.txt. Having said that, i can improve this by deriving |> the MAC address from that file, too.) | |Sure. | |I'm about 98% certain that all of that applies equally as well to the |veth interface inside of the network namespace as it does to the bridge |inside of the network namespace. | |So ... why use a bridge inside of the network namespace? | |I completely get why you use a bridge on the host and the veth interface I do not use a bridge on the host. This i cannot do. |outside of the network namespace. I just don't understand why you are |using a bridge /inside/ the network namespace. But it makes things so easy now. You have seen the scripts, and on the host i see #?0|kent:tmp$ ip rou default via 192.168.0.1 dev wlp1s0 proto dhcp src 192.168.0.153 metric 306 10.0.0.0/8 dev v_n proto kernel scope link src 10.0.0.1 10.0.0.1 dev v_n scope link 192.168.0.0/24 dev wlp1s0 proto dhcp scope link src 192.168.0.153 metric 306 #?0|kent:tmp$ ip a ... 6: wlp1s0: ... inet 192.168.0.153/24 brd 192.168.0.255 scope global dynamic noprefixroute wlp1s0 valid_lft 69766sec preferred_lft 58966sec 8: v_n@if7: ... inet 10.0.0.1/8 scope global v_n valid_lft forever preferred_lft forever and in the namespace #?0|kent:~# ip netns exec v_ns ip rou default via 10.0.0.1 dev v_br 10.0.0.0/8 dev v_br proto kernel scope link src 10.1.0.1 #?0|kent:~# ip netns exec v_ns ip a ... 6: v_br: .. inet 10.1.0.1/8 brd 10.255.255.255 scope global v_br valid_lft forever preferred_lft forever inet6 fe80::dc81:96ff:fe0b:a229/64 scope link valid_lft forever preferred_lft forever 7: v_i@if8: .. link/ether fe:7f:36:b0:04:97 brd ff:ff:ff:ff:ff:ff link-netnsid 0 inet6 fe80::fc7f:36ff:feb0:497/64 scope link valid_lft forever preferred_lft forever And i started a VM for you 8: vm_ulinux-010204: .. link/ether ce:4a:41:5c:d6:61 brd ff:ff:ff:ff:ff:ff inet6 fe80::cc4a:41ff:fe5c:d661/64 scope link valid_lft forever preferred_lft forever No address no route setup, and in the machine $ cat default/net TYPE=static DEV=eth0 ADDR=10.0.1.15 MASK=8 GW=10.0.0.1 Except for using a DHCP server in the namespace this is as short as it can get. Of course if i would use that it would be even less work to do when setting up a VM. And even more flexible and automatic. But, you know, this is so overkill given that i use this only for testing, and dhcpcd is now privilege-separated: #?0|kent:src$ pla|grep dhcpc dhcpcd 509 1 S 0.0 1748 dhcpcd /sbin/dhcpcd -h kent -z wlp1s0 root 510 509 S 0.0 2396 dhcpcd /sbin/dhcpcd -h kent -z wlp1s0 dhcpcd 511 509 S 0.0 268 dhcpcd /sbin/dhcpcd -h kent -z wlp1s0 dhcpcd 512 509 S 0.0 268 dhcpcd /sbin/dhcpcd -h kent -z wlp1s0 dhcpcd 7619 510 S 0.0 376 dhcpcd /sbin/dhcpcd -h kent -z wlp1s0 And this twice all week long for in practice nothing? Ah, no. And what if i move along, i have to have dhcpcd, or configure dnsmasq to serve it for the namespace. And so i can use a simple hosts.txt and have dnsmasq integrate it in its normal DNS service, this would not be that easy if it would be dynamic, i had to look. Anyhow, no network setup at all on in the namespace, i have the hosts.txt that i need anyway, and i configure the machine once i install it. Done. |> Yes. It is just that when you search the internet for Linux and |> bridges you will find mostly brctl or systemd things. (Generally |> spoken the amount of let me say whisked crap is near hundred percent |> in fact.) | |The other thing that I find is how to configure bridging in distro init |scripts. It is terrible. Nothing HOWTO like, not "help the people to help themselves", but everybody who understood a topic by himself is quick in fooling others. This makes the FreeBSD handbook and the BSDs and their manual portfolio in general outstanding. |> Yes. |> |> You have seen all the configuration there is. It is isolated, it is |> not affected by the firewall rules of the host, the firewall rules of |> the host do not take care of this thing at all, attack surface is thus |> only kernel bugs, i thing, and anything on the inside can be hardwired. |> No worries. | |Depending on how you are connecting the host side veth to the network, |there is a very real chance that the host firewall will influence what |goes into / comes out of the emulator in the network namespace |(~container). Particularly if you are routing. Less so if you are |bridging. But bridging can still be effected by the firewall. Don't confuse me please, i am .. not a network expert. Surely you could do use firewall stuff, but i do not. At least nothing special, very restrictive indeed, but 10.0.0.0 is set free early, and other... Ah yes, i have forgotten this line: if [ -n "$VM_NS" ]; then ${iptables} -t nat -A POSTROUTING -o ${what} -j MASQUERADE #echo 1 > /proc/sys/net/ipv4/conf/${what}/proxy_arp fi Here $what is the device, wlp1s0 for example. True. Of course. The comment is a leftover. |> Yes it is cool. The "Linux Advanced Routing & Traffic Control HOWTO" |> (twenty years ago such great things were written and said "Welcome, |> gentle reader", unfortunately that all stopped when the billions |> came over Linux i think, but, of course, today the manual pages are |> great) says | |Ya. The Linux Documentation Project and their How-To's were (arguably |still is) great. It's not /quite/ timeless. But much of the stuff |there is still viable. Some of it is woefully out of date though. Unfortunately yes. ... |> Compared to proxy_arp it was 40 percent here. However, this was |> with kernel 4.19 and the network driver (R8822BE) was in staging, now |> with 5.8 it is not (RTW88) but terribly broken or buggy or whatever. |> It must be said this driver seems to be very complicated, the R8822BE |> had a megabyte of code infrastructure iirc. But it is terrible, |> and now i know that audio via bluetooth and wlan throughput are |> highly dependent. (Or can.) | |Sounds like you've got some issues that I typically don't run into with |more traditional RTL 8129 / 8139 / 8169 drivers. Actually yes. In fact i have booted into 4.19 again today because RTW88 is totally unusable here, at least after the first suspend/resume and even though they added the rtw88_pci.disable_aspm=1 kernel command line switch to work around power management problems. In fact the driver messed the hardware so much that Linux was no longer capable to access it, even booting 4.19 and using R8822BE thus did not do it. By sheer luck the friendly salesman gave me a 512 GB NVME SSD for the price of a 256 GB last year, so i kept the maximally minimized 30 GB Windows partition just for win (imagine that: 30 GB of space .. wasted!), and booted into it, because of despair! Of course i had forgotten my password (i just wanted to log into Windows to see how it looks once i bought the laptop, my last Windows login before that was Windows 95 B), but on the welcome screen you could select the network, and once that dialog wanted the password of the network (!) i rebooted into Linux 4.19 .. and was alive again. Sheer luck, dammit, otherwise i would have been just dead. Terrible! This at least seems to be avoidable by using the above command line switch. Today it could be accessed after reboot. |> I did not know that, will try it out. | |I figured that you would appreciate it. | |> I assign an address to the interface, and make that interface routable |> from the host. | |The fact that the prefix is on a directly attached network should be |sufficient to make it routable to the host. | |Unless you are also using the same 10.0.0.0/8 on the other |{wired,wireless} network that your system is connected to. No. |> This is where all the VMs plug into. | |I disagree. | |The VMs plug into the host bridge. | |I'm asking about why you have a bridge /inside/ of each of the VMs. But i do not? |> That is the other side of the veth interface pair of course. | |Yes. | |But you can use the v_i interface /directly/. I'm not seeing any /need/ |for the bridge /inside/ the network namespace. Yes i understood that. I would need to assign addresses to the VMs once the VM starts, whereas now i only do that inside the VM. Hm?. |> No. The purpose is to be able to create a network of any number |> of VMs somewhere, so those go via the bridge, no? This network is |> self-sufficient |> |> ANY HOST HOWEVER ONLINE <---> VETH -|- VETH IN NAMESPACE |> ^ |> ANY NUMBER OF VMS <-> BRIDGE < |> |> Why would you want to do this? I do not understand. | | +---------------------------------------+ ||host +------+ +-----------+| ||| +---v_ns1---+v_i v_ns1|| |||| +-----------+| |||| +-----------+| |(LAN)---+eth0---+ bri0 +---v_ns2---+v_i v_ns2|| ||||| +-----------+| ||||| +-----------+| |||| +---v_ns3---+v_i v_ns3|| ||| +------+ +-----------+| || +---------------------------------------+ || || +---------------+ |(LAN)---+eth0 notebook| | +---------------+ | |Each network namespace (v_ns#) has it's own vEth pair. The host side of |each vEth pair is connected to the bridge on the host. The bridge on |the host is connected to the host's eth0 interface. Thus, each of the |network namespaces have a layer 2 network connection to the LAN. |Meaning that each of the network namespaces are proper members of the |LAN. No routing is needed. No proxy ARP is needed. Notebook, host, |v_ns1, v_ns2, v_ns3 can all be on the same subnet without doing anything |fancy. There is only one network namespace here. One for all VMs. You cannot create bridge devices on wireless interfaces, unless you have a driver which does support that, or, i guess, you create your own host access point, i dimly recall this could be a solution too. |> Yeah, this is a leftover from the proxy_arp based pseudo-bridge. |> Not to forget it, maybe. I should have removed it before posting. |> I am not a network expert ok, especially not so Linux-specific. | |*nod* | |I was just trying to confirm that's historic. Seeing as how it's |commented out. | |Trying to deduce what, and more so why, can be non-trivial at times. | |> This is just the startup of a VM, it registers at the bridge. | |Yep. Adding the host end of the vEth pair to the host bridge. | |> I am _not_ using proxy_arp no more. This is a leftover, at the |> beginning i made it configurable and could switch in between the |> different approaches via a setting in /x/vm/.run.sh. I should have |> removed it before posting. | |It's cool. Methods, scripts there of, evolve. | |> That one is isolated, i can reach it from the host, and they can talk |> to the host, each other and the internet. I never placed servers |> addressable from the outside in such a thing, this is only a laptop |> without fixed address. I guess in order to allow a public accessible |> server to live in the namespace i would maybe need an ipfilter rule |> on the host. | |Or bridging, as depicted above. ;-) | |> Yes --bind mounting is cool also. But i definetely do not want to |> give the VM an entire /dev, it only needs u?random and that _only_ |> because libcrypt (linked into qemu) needs it, even though it is not |> actually used (the Linux getrandom system call is used instead). | |You can copy the /dev/urandom device, or make a new one, or bind mount |the device inside the network namespace. ;-) | |Even if it's not used for anything other than to make the kernel happy, |you are going to need it. No no, only libgcrypt... |> Yes. But no, i do not really need it, i use it only for qemu |> instances. Interesting would be imposing hard CPU and memory |> restrictions, especially if i would use this approach for creating |> servers, too. This is a future task, however. | |Now you're hedging on cgroups. Yes. That i have to do some time. |> Yeah like i said, i could impose more restrictions on programs running |> inside that namespace, qemu also shows some security flaws at times, |> but this is really just for testing purposes etc. | |IMHO /everything/ has security flaws at one point or another. It's just |a matter of when. Unfortunately true. The complexity of cgroups and the Linux kernel as such is however very, very much intensed compared to a FreeBSD jail. At least once jails appeared it often was nothing more than a "if(process->jailed)" at the beginning of some kernel functions. --steffen | |Der Kragenbaer, The moon bear, |der holt sich munter he cheerfully and one by one |einen nach dem anderen runter wa.ks himself off |(By Robert Gernhardt)

Hello. Sorry for the late reply, very last summer day with cold and rainy days to come, and then i really turned on the TV on a non-Sunday for the first time for long, to watch the German film "Gundermann", which i had on my list ever since i have heard from it. This thread also gives me the feeling of being twisted and wrapped, .. but you know, feelings, pah. Grant Taylor wrote in &lt;b94c3a89-b6ca-b7d4-dd24-ddf7c00283c9(a)spamtrap.tnetconsulting.net&gt;: |On 9/22/20 3:53 PM, Steffen Nurpmeso wrote: ... |> Ha. That could very well be because i was desperately trying to |> create a bridge all the time, but it just was not working at all. ... |Were you trying to bridge things to a wireless NIC? | |> You know, to me this is just a programmatic problem, i just do |> not understand. Why does it matter whether you have eth0 or wlp1s0? | |IMHO the name of the device doesn't matter. | |But the name does imply what type of device it is. eth0 is almost |always wired (but there is no guarantee). After looking it up, wlp1s0 |seems to imply Wi-Fi. | |Wi-Fi tends to imply other problems specific to Wi-Fi. ... |> why can i create a bridge on one but not the other? | |Because some Wi-Fi cards have problems related to multiple MAC |addresses. Problems like they simply refuse to allow them. | |So the problem that it sounds like you're running into is that the Wi-Fi |is refusing to do anything useful with the Ethernet frames that are |being bridged to it. | |Aside: EBTables may be able to help resolve this problem. But that's |another kettle of fish. This i have never used, i do not have it installed. But you mention it -- what i did not understand is why it is not "simply" made a policy that when you want to create a software bridge device, you can create it. In the end i expect the problem to manifest in only a few bytes of data? |> That does not make sense. | |Once you understand some of Wi-Fi's inherent limitations, it should also |make sense to you. Well i never had doubts there are some technical reasons, i just did not know them, and there were no nice error messages nor documentation of the problem. But given that it _does_ work for some drivers i was also sure that the actual problem is more of a notational sort, so to say, and then i did not understand why the creation of a software bridge does not take appropriate steps to make this happen. |> Just do it? | |It (Wi-Fi) probably can't or won't do anything useful with an Ethernet |frame that has a different source MAC address. | |Ergo, bridging with Wi-Fi typically is problematic or simply doesn't |work. It's a limitation of Wi-Fi, not bridging technology. I could say "heck, but if .. |> It works when i inject a VETH pair[.] then it can be done". |> It works when i inject a VETH pair, so may it be like this. But i do not. .. |> I do not use a bridge on the host. This i cannot do. | |I trust that you believe what you are saying. I question the deep |technical merits of it. Including using things like EBTables to NAT* |the source MAC address to that of thee Wi-Fi card. | |*NAT typically applies to layer 3 IP addresses. But the same concept is |being done to layer 3 Ethernet addresses. Well if i had the time and motivation i surely could dive into kernel sources and look around, and maybe even get it (done). But i have so much to do with what other people would call livestock but i call friends, for example, so it seems i am too old and hackneyed to get that job done. ... |I get the lack of motivation for DHCP inside of network namespaces. yeah. |Especially when the IP address(es) used in the network namespace can be |derived from the name of the network namespace. Yes, this is all ssh/scp communication, and that the script handles SSH came with that veth/bridge rewrite, before everything simply had to be typed. And so i need a name or a fixed IP in .ssh/known_hosts. Here i have both now, without much straining. ... |> #?0|kent:src$ pla|grep dhcpc |> dhcpcd 509 1 S 0.0 1748 dhcpcd /sbin/dhcpcd -h kent \ [5x].. |Why do you have as many things running dhcpcd against the same interface? It has to be said that Linux should really offer some kind of setproctitle(2), more and more BSD programs use it to give sense to ps(1) output of privilege-separated programs, and the compatibility code using PR_SET_MM_MAP of prctl(2) after reading and parsing /proc/self/stat is, well, immense effort. ... |> It is terrible. Nothing HOWTO like, not "help the people to help |> themselves", but everybody who understood a topic by himself is quick |> in fooling others. This makes the FreeBSD handbook and the BSDs and |> their manual portfolio in general outstanding. | |Ya. I think that a lot of documentation for things that are post TLDP's |heyday are lacking considerably. | |I've had to dig through a lot of texts, scripts, watch a lot of videos, |read man pages, and do lots of experimentation with network namespaces |to get to where I am now. I'm always happy to share what I know. ... |So it /really/ looks to me like you /do/ have a bridge /inside/ of the |network namespace and that you /are/ using it as part of your |communications path. ... |> There is only one network namespace here. One for all VMs. | |Ah. I had thought there were multiple network namespaces. One per VM / |emulator. No. No, that is really overkill, i am not a student with bad body hygiene having fun with software or something. It is annoying enough that you ever and always again settle on a "that is a good status quo" just to find out the next day that doing it all anew would possibly improve the situation. No. |> You cannot create bridge devices on wireless interfaces, unless you |> have a driver which does support that, or, i guess, you create your |> own host access point, i dimly recall this could be a solution too. | |I don't know if the driver that balks at multiple MACs will support |being an access point. That HostAP software or how it is named, doesn't it deal with this the right way? I seem to have read this is possible. Never tried this. |Though I do wonder if it would be possible to leverage EBTables to play |with MAC addresses to sooth the Wi-Fi NIC's heartburn at multiple MACs. |}:-) Imho "bridge" should do this by itself automatically. ... |> Yes. That [cgroups] i have to do some time. | |I'll look into cgroups some day. I've not had a need to do so yet. Well you could look into software like "containers", you could read If cgroup support, the memory controller and the pids controller are compiled into the kernel, a mounted cgroup2 filesystem can be used to apply memory and process-count limits to a container as it is started. For example, the shell script #!/bin/sh -e echo +memory +pids >/sys/fs/cgroup/cgroup.subtree_control mkdir /sys/fs/cgroup/mycontainer echo $$ >/sys/fs/cgroup/mycontainer/tasks echo 2G >/sys/fs/cgroup/mycontainer/memory.high echo 3G >/sys/fs/cgroup/mycontainer/memory.max echo 2G >/sys/fs/cgroup/mycontainer/memory.swap.max echo 256 >sys/fs/cgroup/mycontainer/pids.max exec contain [...] ... See linux/kernel/Documentation/cgroup-v2.txt for detailed info on the available controllers and configuration parameters. But most of it can be done with unshare and nsenter. For example the super minimal ulinux project (a bit stale) has a box script which does, among other things # shellcheck disable=SC2086 unshare \ --ipc \ --uts \ --pid \ --user \ --fork \ --mount \ --mount-proc \ --map-root-user \ /usr/sbin/chroot "$tmpc/root" \ /usr/bin/env -i $BOX_ENV /bin/sh -c "source /init; $*" It could do nice things like setup_tmpc() { mkdir -p "$tmpc/root" "$tmpc/storage" "$tmpc/work" mount -t overlay \ -o upperdir="$tmpc/storage,lowerdir=/,workdir=$tmpc/work" \ overlayfs "$tmpc/root" I am really interested, but am too lazy to convert the scripts so that this "distribution" (almost kernel-only) can be build without docker etc. |> Unfortunately true. The complexity of cgroups and the Linux kernel |> as such is however very, very much intensed compared to a FreeBSD |> jail. At least once jails appeared it often was nothing more than a |> "if(process->jailed)" at the beginning of some kernel functions. | |*nod* | |I think that Linux still has some things to learn from BSD jails and |Solaris zones. I personally am always astonished when i have contact with Plan9. I cannot really use it, i am too used to BSD/Linux, and some things drive me insane (network configuration etc. is so spreaded). But i am subscribed to the MLs ever since i have been pointed to Plan9 and always wonder when problem solutions happen to happen, how it is done. --steffen | |Der Kragenbaer, The moon bear, |der holt sich munter he cheerfully and one by one |einen nach dem anderen runter wa.ks himself off |(By Robert Gernhardt)