有没有办法获取unix套接字连接另一端的uid

有没有办法让 UNIX 域套接字侦听器仅接受来自特定用户的连接（chmod/chown不适用于抽象套接字 afaik），或者换句话说，获取传入连接的 uid（在 Linux 上）？

Dbus，在Linux上使用抽象unix socket，有一个功能GetConnectionUnixUserpolkit 使用它来确定调用者。所以我想dbus-daemon一定有办法做到这一点。有谁知道这是如何运作的？

检查对等凭据的最简单方法是SO_PEERCRED http://man7.org/linux/man-pages/man7/socket.7.html。 对套接字执行此操作sock:

int len;
struct ucred ucred;

len = sizeof(struct ucred);
if (getsockopt(sock, SOL_SOCKET, SO_PEERCRED, &ucred, &len) == -1)
    // check errno

printf("Credentials from SO_PEERCRED: pid=%ld, euid=%ld, egid=%ld\n",
        (long) ucred.pid, (long) ucred.uid, (long) ucred.gid);

SO_PEERCRED
          Return the credentials of the foreign process connected to
          this socket.  This is possible only for connected AF_UNIX
          stream sockets and AF_UNIX stream and datagram socket pairs
          created using socketpair(2); see unix(7).  The returned
          credentials are those that were in effect at the time of the
          call to connect(2) or socketpair(2).  The argument is a ucred
          structure; define the _GNU_SOURCE feature test macro to obtain
          the definition of that structure from <sys/socket.h>.  This
          socket option is read-only.

From a tlpi http://man7.org/tlpi/ example http://man7.org/tlpi/code/online/dist/sockets/scm_cred_recv.c.html. PostgreSQL http://doxygen.postgresql.org/getpeereid_8c_source.html对于其他 unice 有一些变体。