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/*
devd reads kernel uevents via netlink and for each one spawns the
/etc/hotplug script with an environment consisting of the uevent
keys and values.
After setting up the netlink socket, devd does a double fork to
execute an orphaned /libexec/devd-trigger, which walks /sys/devices,
triggering "add" uevents for each one.
*/
#define _POSIX_C_SOURCE 200809L
#include <errno.h>
#include <stdarg.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdnoreturn.h>
#include <string.h>
#include <fcntl.h>
#include <spawn.h>
#include <sys/socket.h>
#include <sys/wait.h>
#include <unistd.h>
#include <linux/netlink.h>
#define HOTPLUG "/etc/hotplug"
#define TRIGGER "/libexec/devd-trigger"
#define LEN(a) (sizeof(a) / sizeof((a)[0]))
static posix_spawn_file_actions_t fileactions;
static noreturn void
fatal(const char *fmt, ...)
{
va_list ap;
va_start(ap, fmt);
vfprintf(stderr, fmt, ap);
va_end(ap);
if (fmt[0] && fmt[strlen(fmt) - 1] == ':') {
fputc(' ', stderr);
perror(NULL);
} else {
fputc('\n', stderr);
}
exit(1);
}
static int
spawn(char *cmd, char *const env[])
{
int err, status;
pid_t pid;
err = posix_spawn(&pid, cmd, &fileactions, NULL, (char *[]){cmd, NULL}, env);
if (err) {
fprintf(stderr, "spawn %s: %s\n", cmd, strerror(err));
return -1;
}
if (waitpid(pid, &status, 0) == -1) {
fprintf(stderr, "wait %jd: %s\n", (intmax_t)pid, strerror(errno));
return -1;
}
if (!WIFEXITED(status) || WEXITSTATUS(status) != 0)
return -1;
return 0;
}
int
main(int argc, char *argv[])
{
extern char **environ;
int sock, err, status, rcvbuf = 8 * 1024 * 1024;
struct sockaddr_nl addr = {
.nl_family = AF_NETLINK,
.nl_groups = 1,
};
char buf[8192], *var, *eql, *nul, **envp, *env[256];
size_t envlen, envbase;
struct msghdr msg = {
.msg_iov = (struct iovec[]){{buf, sizeof(buf)}},
.msg_iovlen = 1,
};
ssize_t ret;
pid_t pid;
/* setup environment */
envlen = 0;
for (envp = environ; *envp; ++envp) {
if (strncmp(*envp, "PATH=", 5) == 0 ||
strncmp(*envp, "HOME=", 5) == 0)
{
env[envlen++] = *envp;
}
}
envbase = envlen;
/* create spawn file actions for child */
err = posix_spawn_file_actions_init(&fileactions);
if (err) {
perror(NULL);
return 1;
}
err = posix_spawn_file_actions_addopen(&fileactions, 0, "/dev/null", O_RDONLY, 0);
if (err) {
perror(NULL);
return 1;
}
/* open netlink socket */
sock = socket(AF_NETLINK, SOCK_DGRAM | SOCK_CLOEXEC, NETLINK_KOBJECT_UEVENT);
if (sock == -1)
fatal("socket:");
if (setsockopt(sock, SOL_SOCKET, SO_RCVBUFFORCE, &rcvbuf, sizeof(rcvbuf)) == -1)
fatal("setsockopt:");
if (bind(sock, (struct sockaddr *)&addr, sizeof(addr)) == -1)
fatal("bind:");
/* trigger system uevents */
pid = fork();
if (pid == -1)
fatal("fork:");
if (pid == 0) {
err = posix_spawn(&pid, TRIGGER, NULL, NULL, (char *[]){TRIGGER, NULL}, environ);
if (err)
fatal("spawn %s:", TRIGGER);
return 0;
}
if (waitpid(pid, &status, 0) == -1)
fatal("waitpid %jd:", (intmax_t)pid);
if (!WIFEXITED(status) || WEXITSTATUS(status) != 0)
return 1;
next:
for (;;) {
ret = recvmsg(sock, &msg, sizeof(buf));
if (ret == 0)
break;
if (ret == -1)
fatal("recvmsg:");
if (msg.msg_flags & MSG_TRUNC)
continue;
envlen = envbase;
for (var = buf; var < buf + ret; var = nul + 1) {
nul = memchr(var, '\0', ret - (var - buf));
if (!nul) {
fprintf(stderr, "netlink message is not NULL-terminated\n");
goto next;
}
eql = strchr(var, '=');
if (!eql)
continue;
if (envlen == LEN(env) - 1) {
fprintf(stderr, "uevent has too many variables\n");
goto next;
}
env[envlen++] = var;
}
env[envlen] = NULL;
spawn(HOTPLUG, env);
}
}
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