Brief analysis on the user space interception method and implementation of the Uevent event of U-disk and other hot-swappable

#include <stdio.h> #include <string.h> #include <sys/types.h> #include <unistd.h> #include <stdlib.h> #include <sys/socket.h> #include <linux/netlink.h> #define Uevent_msg_len 4096 struct Luther_gliethttp { const char *action; const char *path; const char *subsystem; const char *firmware; int major; int minor; }; static int open_luther_gliethttp_socket (void); static void Parse_event (const char *msg, struct luther_gliethttp *luther_gliethttp); int main (int argc, char* argv[]) { int device_fd =-1; Char msg[uevent_msg_len+2]; int n; DEVICE_FD = Open_luther_gliethttp_socket (); printf ("DEVICE_FD =%d/n", device_fd); do { while ((n = recv (DEVICE_FD, MSG, Uevent_msg_len, 0)) > 0) { struct Luther_gliethttp luther_gliethttp; if (n = = uevent_msg_len)/* Overflow--Discard */ Continue Msg[n] = '/0 '; MSG[N+1] = '/0 '; Parse_event (msg, &luther_gliethttp); } } while (1); } static int open_luther_gliethttp_socket (void) { struct SOCKADDR_NL addr; int sz = 64*1024; int s; memset (&addr, 0, sizeof (addr)); addr.nl_family = Af_netlink; Addr.nl_pid = Getpid (); Addr.nl_groups = 0xFFFFFFFF; s = socket (Pf_netlink, SOCK_DGRAM, netlink_kobject_uevent); if (S < 0) return-1; SetSockOpt (S, Sol_socket, So_rcvbufforce, &sz, sizeof (SZ)); if (Bind (s, (struct sockaddr *) &addr, sizeof (addr)) < 0) { Close (s); return-1; } return s; } static void Parse_event (const char *msg, struct luther_gliethttp *luther_gliethttp) { Luther_gliethttp->action = ""; Luther_gliethttp->path = ""; Luther_gliethttp->subsystem = ""; Luther_gliethttp->firmware = ""; Luther_gliethttp->major =-1; Luther_gliethttp->minor =-1; /* Currently ignoring SEQNUM */ printf ("========================================================/n"); while (*msg) { printf ("%s/n", msg); if (!STRNCMP (msg, "action=", 7)) { msg + = 7; Luther_gliethttp->action = msg; } else if (!STRNCMP (msg, "devpath=", 8)) { msg + = 8; Luther_gliethttp->path = msg; } else if (!STRNCMP (msg, "subsystem=", 10)) { msg + = 10; Luther_gliethttp->subsystem = msg; } else if (!STRNCMP (msg, "firmware=", 9)) { msg + = 9; Luther_gliethttp->firmware = msg; } else if (!STRNCMP (msg, "major=", 6)) { msg + = 6; Luther_gliethttp->major = Atoi (msg); } else if (!STRNCMP (msg, "minor=", 6)) { msg + = 6; Luther_gliethttp->minor = Atoi (msg); } /* advance to after the next/0 */ while (*msg++) ; } printf ("Event {'%s ', '%s ', '%s ', '%s ',%d,%d}/n", Luther_gliethttp->action, Luther_gliethttp->path,luther_gliethttp->subsystem, Luther_gliethttp->firmware, Luther_gliethttp->major,luther_gliethttp->minor); } command, you can use Udevmonitor.