131 lines
3.3 KiB
C
131 lines
3.3 KiB
C
/*
|
|
* Copyright 2015 Denys Vlasenko
|
|
*
|
|
* Licensed under GPLv2, see file LICENSE in this source tree.
|
|
*/
|
|
//config:config UEVENT
|
|
//config: bool "uevent"
|
|
//config: default y
|
|
//config: select PLATFORM_LINUX
|
|
//config: help
|
|
//config: uevent is a netlink listener for kernel uevent notifications
|
|
//config: sent via netlink. It is usually used for dynamic device creation.
|
|
|
|
//applet:IF_UEVENT(APPLET(uevent, BB_DIR_SBIN, BB_SUID_DROP))
|
|
|
|
//kbuild:lib-$(CONFIG_UEVENT) += uevent.o
|
|
|
|
//usage:#define uevent_trivial_usage
|
|
//usage: "[PROG [ARGS]]"
|
|
//usage:#define uevent_full_usage "\n\n"
|
|
//usage: "uevent runs PROG for every netlink notification."
|
|
//usage: "\n""PROG's environment contains data passed from the kernel."
|
|
//usage: "\n""Typical usage (daemon for dynamic device node creation):"
|
|
//usage: "\n"" # uevent mdev & mdev -s"
|
|
|
|
#include "libbb.h"
|
|
#include "common_bufsiz.h"
|
|
#include <linux/netlink.h>
|
|
|
|
#define BUFFER_SIZE 16*1024
|
|
|
|
#define env ((char **)bb_common_bufsiz1)
|
|
#define INIT_G() do { setup_common_bufsiz(); } while (0)
|
|
enum {
|
|
MAX_ENV = COMMON_BUFSIZE / sizeof(env[0]) - 1,
|
|
};
|
|
|
|
#ifndef SO_RCVBUFFORCE
|
|
#define SO_RCVBUFFORCE 33
|
|
#endif
|
|
enum { RCVBUF = 2 * 1024 * 1024 };
|
|
|
|
int uevent_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
|
|
int uevent_main(int argc UNUSED_PARAM, char **argv)
|
|
{
|
|
struct sockaddr_nl sa;
|
|
int fd;
|
|
|
|
INIT_G();
|
|
|
|
argv++;
|
|
|
|
// Subscribe for UEVENT kernel messages
|
|
sa.nl_family = AF_NETLINK;
|
|
sa.nl_pad = 0;
|
|
sa.nl_pid = getpid();
|
|
sa.nl_groups = 1 << 0;
|
|
fd = xsocket(AF_NETLINK, SOCK_DGRAM, NETLINK_KOBJECT_UEVENT);
|
|
xbind(fd, (struct sockaddr *) &sa, sizeof(sa));
|
|
close_on_exec_on(fd);
|
|
|
|
// Without a sufficiently big RCVBUF, a ton of simultaneous events
|
|
// can trigger ENOBUFS on read, which is unrecoverable.
|
|
// Reproducer:
|
|
// uevent mdev &
|
|
// find /sys -name uevent -exec sh -c 'echo add >"{}"' ';'
|
|
//
|
|
// SO_RCVBUFFORCE (root only) can go above net.core.rmem_max sysctl
|
|
setsockopt_SOL_SOCKET_int(fd, SO_RCVBUF, RCVBUF);
|
|
setsockopt_SOL_SOCKET_int(fd, SO_RCVBUFFORCE, RCVBUF);
|
|
if (0) {
|
|
int z;
|
|
socklen_t zl = sizeof(z);
|
|
getsockopt(fd, SOL_SOCKET, SO_RCVBUF, &z, &zl);
|
|
bb_error_msg("SO_RCVBUF:%d", z);
|
|
}
|
|
|
|
for (;;) {
|
|
char *netbuf;
|
|
char *s, *end;
|
|
ssize_t len;
|
|
int idx;
|
|
|
|
// In many cases, a system sits for *days* waiting
|
|
// for a new uevent notification to come in.
|
|
// We use a fresh mmap so that buffer is not allocated
|
|
// until kernel actually starts filling it.
|
|
netbuf = mmap(NULL, BUFFER_SIZE,
|
|
PROT_READ | PROT_WRITE,
|
|
MAP_PRIVATE | MAP_ANON,
|
|
/* ignored: */ -1, 0);
|
|
if (netbuf == MAP_FAILED)
|
|
bb_perror_msg_and_die("mmap");
|
|
|
|
// Here we block, possibly for a very long time
|
|
len = safe_read(fd, netbuf, BUFFER_SIZE - 1);
|
|
if (len < 0)
|
|
bb_perror_msg_and_die("read");
|
|
end = netbuf + len;
|
|
*end = '\0';
|
|
|
|
// Each netlink message starts with "ACTION@/path"
|
|
// (which we currently ignore),
|
|
// followed by environment variables.
|
|
if (!argv[0])
|
|
putchar('\n');
|
|
idx = 0;
|
|
s = netbuf;
|
|
while (s < end) {
|
|
if (!argv[0])
|
|
puts(s);
|
|
if (strchr(s, '=') && idx < MAX_ENV)
|
|
env[idx++] = s;
|
|
s += strlen(s) + 1;
|
|
}
|
|
env[idx] = NULL;
|
|
|
|
idx = 0;
|
|
while (env[idx])
|
|
putenv(env[idx++]);
|
|
if (argv[0])
|
|
spawn_and_wait(argv);
|
|
idx = 0;
|
|
while (env[idx])
|
|
bb_unsetenv(env[idx++]);
|
|
munmap(netbuf, BUFFER_SIZE);
|
|
}
|
|
|
|
return 0; // not reached
|
|
}
|