Alexander Mikhalitsyn wrote:
> Add SO_PEERCGROUPID which allows to get cgroup_id
> for a socket.
>
> We already have analogical interfaces to retrieve this
> information:
> - inet_diag: INET_DIAG_CGROUP_ID
> - eBPF: bpf_sk_cgroup_id
>
> Having getsockopt() interface makes sense for many
> applications, because using eBPF is not always an option,
> while inet_diag has obvious complexety and performance drawbacks
> if we only want to get this specific info for one specific socket.
>
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Cc: netdev@xxxxxxxxxxxxxxx
> Cc: cgroups@xxxxxxxxxxxxxxx
> Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
> Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
> Cc: Jakub Kicinski <kuba@xxxxxxxxxx>
> Cc: Paolo Abeni <pabeni@xxxxxxxxxx>
> Cc: Willem de Bruijn <willemb@xxxxxxxxxx>
> Cc: Leon Romanovsky <leon@xxxxxxxxxx>
> Cc: Arnd Bergmann <arnd@xxxxxxxx>
> Cc: Christian Brauner <brauner@xxxxxxxxxx>
> Cc: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
> Cc: Lennart Poettering <mzxreary@xxxxxxxxxxx>
> Cc: Luca Boccassi <bluca@xxxxxxxxxx>
> Cc: Tejun Heo <tj@xxxxxxxxxx>
> Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
> Cc: "Michal Koutný" <mkoutny@xxxxxxxx>
> Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@xxxxxxxxxxxxx>
> ---
> 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 | 17 +++++++
> net/unix/af_unix.c | 63 +++++++++++++++++++++++++
> tools/include/uapi/asm-generic/socket.h | 2 +
> 8 files changed, 92 insertions(+)
>
> diff --git a/arch/alpha/include/uapi/asm/socket.h b/arch/alpha/include/uapi/asm/socket.h
> index 3df5f2dd4c0f..58ce457b2c09 100644
> --- a/arch/alpha/include/uapi/asm/socket.h
> +++ b/arch/alpha/include/uapi/asm/socket.h
> @@ -150,6 +150,8 @@
>
> #define SO_RCVPRIORITY 82
>
> +#define SO_PEERCGROUPID 83
> +
> #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 22fa8f19924a..823fa67f7d79 100644
> --- a/arch/mips/include/uapi/asm/socket.h
> +++ b/arch/mips/include/uapi/asm/socket.h
> @@ -161,6 +161,8 @@
>
> #define SO_RCVPRIORITY 82
>
> +#define SO_PEERCGROUPID 83
> +
> #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 aa9cd4b951fe..1ee2e858d177 100644
> --- a/arch/parisc/include/uapi/asm/socket.h
> +++ b/arch/parisc/include/uapi/asm/socket.h
> @@ -142,6 +142,8 @@
>
> #define SO_RCVPRIORITY 0x404D
>
> +#define SO_PEERCGROUPID 0x404E
> +
> #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 5b464a568664..2fe7d0c48a63 100644
> --- a/arch/sparc/include/uapi/asm/socket.h
> +++ b/arch/sparc/include/uapi/asm/socket.h
> @@ -143,6 +143,8 @@
>
> #define SO_RCVPRIORITY 0x005b
>
> +#define SO_PEERCGROUPID 0x005c
> +
> #if !defined(__KERNEL__)
>
>
> diff --git a/include/uapi/asm-generic/socket.h b/include/uapi/asm-generic/socket.h
> index aa5016ff3d91..903904bb537c 100644
> --- a/include/uapi/asm-generic/socket.h
> +++ b/include/uapi/asm-generic/socket.h
> @@ -145,6 +145,8 @@
>
> #define SO_RCVPRIORITY 82
>
> +#define SO_PEERCGROUPID 83
> +
> #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 a0598518ce89..6dc0b1a8367b 100644
> --- a/net/core/sock.c
> +++ b/net/core/sock.c
> @@ -1946,6 +1946,23 @@ int sk_getsockopt(struct sock *sk, int level, int optname,
> goto lenout;
> }
>
> +#ifdef CONFIG_SOCK_CGROUP_DATA
> + case SO_PEERCGROUPID:
> + {
> + const struct proto_ops *ops;
> +
> + if (sk->sk_family != AF_UNIX)
> + return -EOPNOTSUPP;
> +
> + ops = READ_ONCE(sock->ops);
> + if (!ops->getsockopt)
> + return -EOPNOTSUPP;
> +
> + return ops->getsockopt(sock, SOL_SOCKET, optname, optval.user,
> + optlen.user);
> + }
> +#endif
> +
> /* Dubious BSD thing... Probably nobody even uses it, but
> * the UNIX standard wants it for whatever reason... -DaveM
> */
> diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
> index 2b2c0036efc9..3455f38f033d 100644
> --- a/net/unix/af_unix.c
> +++ b/net/unix/af_unix.c
> @@ -901,6 +901,66 @@ static void unix_show_fdinfo(struct seq_file *m, struct socket *sock)
> #define unix_show_fdinfo NULL
> #endif
>
> +static int unix_getsockopt(struct socket *sock, int level, int optname,
> + char __user *optval, int __user *optlen)
> +{
> + struct sock *sk = sock->sk;
> +
> + union {
> + int val;
> + u64 val64;
> + } v;
> +
> + int lv = sizeof(int);
> + int len;
why the union if the only valid use is a u64? Is this forward looking?
