On Fri, Dec 13, 2019 at 03:11:54PM +0800, ning....@zte.com.cn wrote: > > This can be done efficiently as follows: > > 1. kata-runtime listens on a vsock port > > 2. kata-agent-port=PORT is added to the kernel command-line options > > 3. kata-agent parses the port number and connects to the host > > > > This eliminates the reconnection attempts. > > There will be an additional problem if do this: > Who decides which port the `runtime` should listen?
Let the host kernel automatically assign a port using VMADDR_PORT_ANY.
It works like this:
struct sockaddr_vm svm = {
.svm_family = AF_VSOCK,
.svm_port = VMADDR_PORT_ANY,
.svm_cid = VMADDR_CID_ANY,
};
int fd = socket(AF_VSOCK, SOCK_STREAM, 0);
...
if (bind(fd, (const struct sockaddr *)&svm, sizeof(svm)) < 0) {
...
}
socklen_t socklen = sizeof(svm);
if (getsockname(fd, (struct sockaddr *)&svm, &socklen) < 0) {
...
}
printf("cid %u port %u\n", svm.svm_cid, svm.svm_port);
> Consider the worst case:
> The ports selected by two `runtime` running in parallel always conflict,
> and this case is unavoidable, even if we can reduce the possibility of
> conflicts through algorithms.
> Because we don't have a daemon that can allocate unique port to `runtime`.
The kernel assigns unique ports and only fails if the entire port
namespace is exhausted. The port namespace is 32-bits so this is not a
real-world concern.
Does this information clarify how the runtime can connect to the guest
agent without loops or delays?
Stefan
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