• Martynas Pumputis's avatar
    net: retrieve netns cookie via getsocketopt · e8b9eab9
    Martynas Pumputis authored
    It's getting more common to run nested container environments for
    testing cloud software. One of such examples is Kind [1] which runs a
    Kubernetes cluster in Docker containers on a single host. Each container
    acts as a Kubernetes node, and thus can run any Pod (aka container)
    inside the former. This approach simplifies testing a lot, as it
    eliminates complicated VM setups.
    
    Unfortunately, such a setup breaks some functionality when cgroupv2 BPF
    programs are used for load-balancing. The load-balancer BPF program
    needs to detect whether a request originates from the host netns or a
    container netns in order to allow some access, e.g. to a service via a
    loopback IP address. Typically, the programs detect this by comparing
    netns cookies with the one of the init ns via a call to
    bpf_get_netns_cookie(NULL). However, in nested environments the latter
    cannot be used given the Kubernetes node's netns is outside the init ns.
    To fix this, we need to pass the Kubernetes node netns cookie to the
    program in a different way: by extending getsockopt() with a
    SO_NETNS_COOKIE option, the orchestrator which runs in the Kubernetes
    node netns can retrieve the cookie and pass it to the program instead.
    
    Thus, this is following up on Eric's commit 3d368ab8 ("net:
    initialize net->net_cookie at netns setup") to allow retrieval via
    SO_NETNS_COOKIE.  This is also in line in how we retrieve socket cookie
    via SO_COOKIE.
    
      [1] https://kind.sigs.k8s.io/Signed-off-by: default avatarLorenz Bauer <lmb@cloudflare.com>
    Signed-off-by: default avatarMartynas Pumputis <m@lambda.lt>
    Cc: Eric Dumazet <edumazet@google.com>
    Reviewed-by: default avatarEric Dumazet <edumazet@google.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    e8b9eab9
socket.h 3.8 KB