Vlad Yasevich wrote: > Hi Daniel > >> Hi all, >> >> Dmitry and I, we thought about a possible implementation allowing the >> l2/l3 to coexists. >> >> The idea is assuming the l3 network namespaces are the leaf in the l2 >> namespace hierarchy tree. By default, init process is l2 namespace. From >> a layer 3, it is impossible to do a new network namespace unshare. >> >> All the configuration is done into the l2 namespace. When a l3 is >> created a new IP address should be created into the l2 namespace and >> "pushed" into the l3. When the l3 dies, the IP is pulled to its parent, >> aka the l2. In order to ensure security into the l3, the NET_ADMIN >> capability is lost when doing unsharing for l3. >> There is no extra code for socket virtualization. It is a common part. >> >> How to setup a l3 namespace ? >> ----------------------------- >> >> 1 - setup a new IP address in l2 namespace >> 2 - create a l3 namespace >> 3 - specific socket ioctl to "push" the IP address from the l2 >> namespace to the newly created l3 namespace > > This means that there is some kind of identifier for the l3 namespace, right? Not exactly. The bind_ns allows to assign an identifier to a namespace. The namespace is an aggregation of the different namespace ressources (ipc, pid, net, utsname, ...). But the result is the same, we use the namespace identifier instead of a l3 namespace identifier. > >> The l2 lose visibility on the IP address and l3 gains visibility on the >> IP address. A ifconfig or a ip command shows only the IP address >> assigned to the namespace. Loopback address is always visible. > > Hmm.... I've been thinking about this, and I think this OK from the sockets point > of view, i.e. binds() in l2 lose visibility to the new l3 address. There is > a concern for a potential race here though. Do you mean, someone in the l2 namespace can use the IP address before pushing it the l3 namespace ? That is right, perhaps the call should be done in one shoot (set address + pushing it to l3) > However, it would be really nice to be able to see l3 namespace addresses in > the parent l2 tagged in some way. > >> How to handle outgoing traffic ? >> -------------------------------- >> >> The bind must be checked with the IP addresses belonging to the l3 >> namespace and with all the derivative addresses (multicast, broadcast, >> zero net, loopback, ...). >> >> The IP addresses will rely on aliased IP address. The source address >> must be filled with the IP address belonging the l3 namespace when not >> set. This is a trivial operation, because we know which IP addresses are >> assigned to the l3 namespace. > > Can you provide a little more info? I think I already answered this question in the previous email. I am afraid this paragraph is not very clear ... ;) > >> When the route are resolved, the l3 namespace switch the its parent, >> that is to say the l2 namespace, and the virtualization follows its >> normal path. >> >> How to handle incoming traffic ? >> -------------------------------- >> >> Because we can have several sockets listening on the same >> INADDR_ANY:port, we must find the network namespace associated with the >> destination IP address. >> For unicast, this is a trivial operation, because that can be checked >> with the assigned IP address again. For broadcast and multicast, some >> extra work should be done in order to store the namespaces which are >> listening on a broadcast address. As soon as the namespace is found, we >> switch to it. This can be done with netfilters. > > The problem is with multicasts. Multicast groups are joined on the interface > bases. Every socket that bound *:multicast_port will receive multicast > traffic once a single app joined the group. Since l3 namespaces don't have > share the conceptual interface, theoretically, all l3 namespaces should receive > multicast traffic. Right. You sunk my battleship :) Need to be thought... > >> Routes and co. >> -------------- >> >> - Routes: they are not isolated, each l3 namespace can see all the >> routes from the other namespaces. That allows the routing engine to see >> all the routes and choose the loopback when two network namespaces in >> the same host try to communicate. >> >> - Cache: the routing cache must be isolated, otherwise the socket >> isolation will not work. The l3 namespace code does not impact the l2 >> namespace code and route cache isolation is a common part if the l3 >> namespace switching is done in the right place. >> >> >> Dmitry has posted the l2 namespace relying on the net namespace empty >> framework, I will post the l3 namespace relying on the l2 namespace >> today or tomorrow. >> > > Looking forward to it. Fixing a kref problem... Thanks for all your comments. -- Daniel