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Subject[PATCH bpf 1/4] net: add SO_NETNS_COOKIE socket option
Date
We need to distinguish which network namespace a socket belongs to.
BPF has the useful bpf_get_netns_cookie helper for this, but accessing
it from user space isn't possible. Add a read-only socket option that
returns the netns cookie, similar to SO_COOKIE. If network namespaces
are disabled, SO_NETNS_COOKIE returns the cookie of init_net.

The BPF helpers change slightly: instead of returning 0 when network
namespaces are disabled we return the init_net cookie as for the
socket option.

Cc: linux-api@vger.kernel.org
Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>
---
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/linux/sock_diag.h | 20 ++++++++++++++++++++
include/uapi/asm-generic/socket.h | 2 ++
net/core/filter.c | 9 ++++-----
net/core/sock.c | 7 +++++++
8 files changed, 41 insertions(+), 5 deletions(-)

diff --git a/arch/alpha/include/uapi/asm/socket.h b/arch/alpha/include/uapi/asm/socket.h
index 57420356ce4c..6b3daba60987 100644
--- a/arch/alpha/include/uapi/asm/socket.h
+++ b/arch/alpha/include/uapi/asm/socket.h
@@ -127,6 +127,8 @@
#define SO_PREFER_BUSY_POLL 69
#define SO_BUSY_POLL_BUDGET 70

+#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 2d949969313b..cdf404a831b2 100644
--- a/arch/mips/include/uapi/asm/socket.h
+++ b/arch/mips/include/uapi/asm/socket.h
@@ -138,6 +138,8 @@
#define SO_PREFER_BUSY_POLL 69
#define SO_BUSY_POLL_BUDGET 70

+#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 f60904329bbc..5b5351cdcb33 100644
--- a/arch/parisc/include/uapi/asm/socket.h
+++ b/arch/parisc/include/uapi/asm/socket.h
@@ -119,6 +119,8 @@
#define SO_PREFER_BUSY_POLL 0x4043
#define SO_BUSY_POLL_BUDGET 0x4044

+#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 848a22fbac20..ff79db753dce 100644
--- a/arch/sparc/include/uapi/asm/socket.h
+++ b/arch/sparc/include/uapi/asm/socket.h
@@ -120,6 +120,8 @@
#define SO_PREFER_BUSY_POLL 0x0048
#define SO_BUSY_POLL_BUDGET 0x0049

+#define SO_NETNS_COOKIE 0x004a
+
#if !defined(__KERNEL__)


diff --git a/include/linux/sock_diag.h b/include/linux/sock_diag.h
index 0b9ecd8cf979..6e88436097b1 100644
--- a/include/linux/sock_diag.h
+++ b/include/linux/sock_diag.h
@@ -38,6 +38,26 @@ static inline u64 sock_gen_cookie(struct sock *sk)
return cookie;
}

+static inline u64 __sock_gen_netns_cookie(struct sock *sk)
+{
+#ifdef CONFIG_NET_NS
+ return __net_gen_cookie(sk->sk_net.net);
+#else
+ return __net_gen_cookie(&init_net);
+#endif
+}
+
+static inline u64 sock_gen_netns_cookie(struct sock *sk)
+{
+ u64 cookie;
+
+ preempt_disable();
+ cookie = __sock_gen_netns_cookie(sk);
+ preempt_enable();
+
+ return cookie;
+}
+
int sock_diag_check_cookie(struct sock *sk, const __u32 *cookie);
void sock_diag_save_cookie(struct sock *sk, __u32 *cookie);

diff --git a/include/uapi/asm-generic/socket.h b/include/uapi/asm-generic/socket.h
index 4dcd13d097a9..d588c244ec2f 100644
--- a/include/uapi/asm-generic/socket.h
+++ b/include/uapi/asm-generic/socket.h
@@ -122,6 +122,8 @@
#define SO_PREFER_BUSY_POLL 69
#define SO_BUSY_POLL_BUDGET 70

+#define SO_NETNS_COOKIE 71
+
#if !defined(__KERNEL__)

#if __BITS_PER_LONG == 64 || (defined(__x86_64__) && defined(__ILP32__))
diff --git a/net/core/filter.c b/net/core/filter.c
index e15d4741719a..51f47b6913f1 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -4645,11 +4645,10 @@ static const struct bpf_func_proto bpf_get_socket_cookie_sock_ops_proto = {

static u64 __bpf_get_netns_cookie(struct sock *sk)
{
-#ifdef CONFIG_NET_NS
- return __net_gen_cookie(sk ? sk->sk_net.net : &init_net);
-#else
- return 0;
-#endif
+ if (sk)
+ return __sock_gen_netns_cookie(sk);
+
+ return __net_gen_cookie(&init_net);
}

BPF_CALL_1(bpf_get_netns_cookie_sock, struct sock *, ctx)
diff --git a/net/core/sock.c b/net/core/sock.c
index bbcd4b97eddd..2db201c210ca 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1606,6 +1606,13 @@ 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 = sock_gen_netns_cookie(sk);
+ break;
+
default:
/* We implement the SO_SNDLOWAT etc to not be settable
* (1003.1g 7).
--
2.27.0
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