From: Martynas Pumputis m@lambda.lt
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 3d368ab87cf6 ("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.
Signed-off-by: Lorenz Bauer lmb@cloudflare.com Signed-off-by: Martynas Pumputis m@lambda.lt Cc: Eric Dumazet edumazet@google.com Reviewed-by: Eric Dumazet edumazet@google.com Signed-off-by: David S. Miller davem@davemloft.net (cherry picked from commit e8b9eab99232c4e62ada9d7976c80fd5e8118289) --- arch/alpha/include/uapi/asm/socket.h | 2 ++ arch/mips/include/uapi/asm/socket.h | 2 ++ arch/parisc/include/uapi/asm/socket.h | 2 ++ arch/sparc/include/uapi/asm/socket.h | 2 ++ include/uapi/asm-generic/socket.h | 2 ++ net/core/sock.c | 7 +++++++ 6 files changed, 17 insertions(+)
diff --git a/arch/alpha/include/uapi/asm/socket.h b/arch/alpha/include/uapi/asm/socket.h index de6c4df61082..d033d3f92d6d 100644 --- a/arch/alpha/include/uapi/asm/socket.h +++ b/arch/alpha/include/uapi/asm/socket.h @@ -124,6 +124,8 @@
#define SO_DETACH_REUSEPORT_BPF 68
+#define SO_NETNS_COOKIE 71 + #if !defined(__KERNEL__)
#if __BITS_PER_LONG == 64 diff --git a/arch/mips/include/uapi/asm/socket.h b/arch/mips/include/uapi/asm/socket.h index d0a9ed2ca2d6..ff3ab771e769 100644 --- a/arch/mips/include/uapi/asm/socket.h +++ b/arch/mips/include/uapi/asm/socket.h @@ -135,6 +135,8 @@
#define SO_DETACH_REUSEPORT_BPF 68
+#define SO_NETNS_COOKIE 71 + #if !defined(__KERNEL__)
#if __BITS_PER_LONG == 64 diff --git a/arch/parisc/include/uapi/asm/socket.h b/arch/parisc/include/uapi/asm/socket.h index 10173c32195e..1a8ec3838c9b 100644 --- a/arch/parisc/include/uapi/asm/socket.h +++ b/arch/parisc/include/uapi/asm/socket.h @@ -116,6 +116,8 @@
#define SO_DETACH_REUSEPORT_BPF 0x4042
+#define SO_NETNS_COOKIE 0x4045 + #if !defined(__KERNEL__)
#if __BITS_PER_LONG == 64 diff --git a/arch/sparc/include/uapi/asm/socket.h b/arch/sparc/include/uapi/asm/socket.h index 8029b681fc7c..08f9bbbf5bf2 100644 --- a/arch/sparc/include/uapi/asm/socket.h +++ b/arch/sparc/include/uapi/asm/socket.h @@ -117,6 +117,8 @@
#define SO_DETACH_REUSEPORT_BPF 0x0047
+#define SO_NETNS_COOKIE 0x0050 + #if !defined(__KERNEL__)
diff --git a/include/uapi/asm-generic/socket.h b/include/uapi/asm-generic/socket.h index 77f7c1638eb1..645606824258 100644 --- a/include/uapi/asm-generic/socket.h +++ b/include/uapi/asm-generic/socket.h @@ -119,6 +119,8 @@
#define SO_DETACH_REUSEPORT_BPF 68
+#define SO_NETNS_COOKIE 71 + #if !defined(__KERNEL__)
#if __BITS_PER_LONG == 64 || (defined(__x86_64__) && defined(__ILP32__)) diff --git a/net/core/sock.c b/net/core/sock.c index 0506590b016b..64e2f9fb6552 100644 --- a/net/core/sock.c +++ b/net/core/sock.c @@ -1613,6 +1613,13 @@ int sock_getsockopt(struct socket *sock, int level, int optname, v.val = sk->sk_bound_dev_if; break;
+ case SO_NETNS_COOKIE: + lv = sizeof(u64); + if (len != lv) + return -EINVAL; + v.val64 = atomic64_read(&sock_net(sk)->net_cookie); + break; + default: /* We implement the SO_SNDLOWAT etc to not be settable * (1003.1g 7).