On Sun, Jul 6, 2025 at 7:02 AM Willem de Bruijn
[off-list ref] wrote:
Kuniyuki Iwashima wrote:
quoted
We have an application that uses almost the same code for TCP and
AF_UNIX (SOCK_STREAM).
TCP can use TCP_INQ, but AF_UNIX doesn't have it and requires an
extra syscall, ioctl(SIOCINQ) or getsockopt(SO_MEMINFO) as an
alternative.
Let's introduce the generic version of TCP_INQ.
If SO_INQ is enabled, recvmsg() will put a cmsg of SCM_INQ that
contains the exact value of ioctl(SIOCINQ). The cmsg is also
included when msg->msg_get_inq is non-zero to make sockets
io_uring-friendly.
Note that SOCK_CUSTOM_SOCKOPT is flagged only for SOCK_STREAM to
override setsockopt() for SOL_SOCKET.
By having the flag in struct unix_sock, instead of struct sock, we
can later add SO_INQ support for TCP and reuse tcp_sk(sk)->recvmsg_inq.
Note also that supporting custom getsockopt() for SOL_SOCKET will need
preparation for other SOCK_CUSTOM_SOCKOPT users (UDP, vsock, MPTCP).
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
quoted
+static int unix_setsockopt(struct socket *sock, int level, int optname,
+ sockptr_t optval, unsigned int optlen)
+{
+ struct unix_sock *u = unix_sk(sock->sk);
+ struct sock *sk = sock->sk;
+ int val;
+
+ if (level != SOL_SOCKET)
+ return -EOPNOTSUPP;
+
+ if (!unix_custom_sockopt(optname))
+ return sock_setsockopt(sock, level, optname, optval, optlen);
+
+ if (optlen != sizeof(int))
+ return -EINVAL;
+
+ if (copy_from_sockptr(&val, optval, sizeof(val)))
+ return -EFAULT;
+
+ switch (optname) {
+ case SO_INQ:
+ if (sk->sk_type != SOCK_STREAM)
+ return -EINVAL;
Sanity check, but technically not needed as SOCK_CUSTOM_SOCKOPT is
only set for SOCK_STREAM?
Yes, I planned to move other AF_UNIX specific options and reuse
unix_setsockopt() for DGRAM and SEQPACKET.
quoted
+
+ if (val > 1 || val < 0)
+ return -EINVAL;
+
+ WRITE_ONCE(u->recvmsg_inq, val);
+ break;
+ default:
+ return -ENOPROTOOPT;
+ }
+
+ return 0;
+}
+