revert(stack-select): drop ff_host_socket bypass that abandoned F-Stack

ff_socket(SOCK_KERNEL) wrongly routed to a raw host socket, bypassing the
F-Stack user-space stack entirely. Revert ff_host_socket and the ff_socket
bypass branch to restore the clean F-Stack path; coexistence will be redone
(hook FF_KERNEL_EVENT baseline + native unified-event) per the reworked spec.

Author: jfb8856606

lib/ff_host_interface.c

@@ -35,7 +35,6 @@
 #include <stdlib.h>
 #include <sys/mman.h>
 #include <sys/stat.h>
-#include <sys/socket.h>
 #include <pthread.h>
 #include <sched.h>
 #include <time.h>
@@ -236,12 +235,6 @@ char *ff_getenv(const char *name)
     return getenv(name);
 }
 
-int
-ff_host_socket(int domain, int type, int protocol)
-{
-    return socket(domain, type, protocol);
-}
-
 void ff_os_errno(int error)
 {
     switch (error) {

lib/ff_host_interface.h

@@ -91,14 +91,5 @@ int ff_rss_tbl_get_portrange(uint32_t saddr, uint32_t daddr, uint16_t sport,
 
 void ff_swi_net_excute(void);
 
-/*
- * Host kernel-stack helpers for connection-level stack selection.
- *   ff_host_socket(): create a socket on the host Linux kernel stack.
- *   ff_default_stack_is_kernel(): returns non-zero when config.ini
- *       [stack] default_stack == kernel for this process.
- */
-int ff_host_socket(int domain, int type, int protocol);
-int ff_default_stack_is_kernel(void);
-
 #endif
 

lib/ff_syscall_wrapper.c

@@ -914,22 +914,6 @@ ff_socket(int domain, int type, int protocol)
 {
     int rc;
     struct socket_args sa;
-
-    /*
-     * Stack selection (M3/M4): route this socket to the host Linux kernel
-     * stack when it carries an explicit SOCK_KERNEL marker (without
-     * SOCK_FSTACK), or when no marker is set and the process default stack is
-     * "kernel" (config.ini [stack] default_stack=kernel). The returned fd is a
-     * host kernel fd; in native ff_api mode it must be used with host syscalls
-     * (bind/listen/connect/epoll/...), not ff_*, since native mode has no
-     * per-fd ownership routing (see docs/kernel_event_support_spec/zh_cn).
-     * The default / SOCK_FSTACK path below stays unchanged (no regression).
-     */
-    if (!(type & SOCK_FSTACK) &&
-        ((type & SOCK_KERNEL) || ff_default_stack_is_kernel())) {
-        return ff_host_socket(domain, type & ~SOCK_KERNEL, protocol);
-    }
-
     sa.domain = domain == LINUX_AF_INET6 ? AF_INET6 : domain;
     sa.type = linux2freebsd_socket_flags(type);
     sa.protocol = protocol;