Initial commit

14 files changed, 1253 insertions, 0 deletions

diff --git a/src/supervision/deps-exe/s6-supervise b/src/supervision/deps-exe/s6-supervise
new file mode 100644
index 0000000..58a34e0
--- /dev/null
+++ b/src/supervision/deps-exe/s6-supervise
@@ -0,0 +1,3 @@
+-ls6
+-lskarnet
+${TAINNOW_LIB}
diff --git a/src/supervision/deps-exe/s6-svc b/src/supervision/deps-exe/s6-svc
new file mode 100644
index 0000000..83cec1e
--- /dev/null
+++ b/src/supervision/deps-exe/s6-svc
@@ -0,0 +1,2 @@
+-ls6
+-lskarnet
diff --git a/src/supervision/deps-exe/s6-svok b/src/supervision/deps-exe/s6-svok
new file mode 100644
index 0000000..e7187fe
--- /dev/null
+++ b/src/supervision/deps-exe/s6-svok
@@ -0,0 +1 @@
+-lskarnet
diff --git a/src/supervision/deps-exe/s6-svscan b/src/supervision/deps-exe/s6-svscan
new file mode 100644
index 0000000..58a34e0
--- /dev/null
+++ b/src/supervision/deps-exe/s6-svscan
@@ -0,0 +1,3 @@
+-ls6
+-lskarnet
+${TAINNOW_LIB}
diff --git a/src/supervision/deps-exe/s6-svscanctl b/src/supervision/deps-exe/s6-svscanctl
new file mode 100644
index 0000000..83cec1e
--- /dev/null
+++ b/src/supervision/deps-exe/s6-svscanctl
@@ -0,0 +1,2 @@
+-ls6
+-lskarnet
diff --git a/src/supervision/deps-exe/s6-svstat b/src/supervision/deps-exe/s6-svstat
new file mode 100644
index 0000000..7065b26
--- /dev/null
+++ b/src/supervision/deps-exe/s6-svstat
@@ -0,0 +1,3 @@
+-ls6
+-lskarnet
+${SYSCLOCK_LIB}
diff --git a/src/supervision/deps-exe/s6-svwait b/src/supervision/deps-exe/s6-svwait
new file mode 100644
index 0000000..58a34e0
--- /dev/null
+++ b/src/supervision/deps-exe/s6-svwait
@@ -0,0 +1,3 @@
+-ls6
+-lskarnet
+${TAINNOW_LIB}
diff --git a/src/supervision/s6-supervise.c b/src/supervision/s6-supervise.c
new file mode 100644
index 0000000..f9a9872
--- /dev/null
+++ b/src/supervision/s6-supervise.c
@@ -0,0 +1,508 @@
+/* ISC license. */
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/wait.h>
+#include <unistd.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <signal.h>
+#include <skalibs/allreadwrite.h>
+#include <skalibs/bytestr.h>
+#include <skalibs/uint.h>
+#include <skalibs/strerr2.h>
+#include <skalibs/tai.h>
+#include <skalibs/iopause.h>
+#include <skalibs/djbunix.h>
+#include <skalibs/sig.h>
+#include <skalibs/selfpipe.h>
+#include <skalibs/environ.h>
+#include <skalibs/skamisc.h>
+#include <s6/ftrigw.h>
+#include <s6/s6-supervise.h>
+
+#define USAGE "s6-supervise dir"
+
+typedef enum trans_e trans_t, *trans_t_ref ;
+enum trans_e
+{
+  V_TIMEOUT, V_CHLD, V_TERM, V_HUP, V_QUIT,
+  V_a, V_b, V_q, V_h, V_k, V_t, V_i, V_1, V_2, V_f, V_F, V_p, V_c,
+  V_o, V_d, V_u, V_x, V_O
+} ;
+
+typedef enum state_e state_t, *state_t_ref ;
+enum state_e
+{
+  DOWN,
+  UP,
+  FINISH,
+  LASTUP,
+  LASTFINISH
+} ;
+
+typedef void action_t (void) ;
+typedef action_t *action_t_ref ;
+
+static tain_t deadline ;
+static s6_svstatus_t status = { .stamp = TAIN_ZERO, .pid = 0, .flagwant = 1, .flagwantup = 1, .flagpaused = 0, .flagfinishing = 0 } ;
+static state_t state = DOWN ;
+static int flagsetsid = 1 ;
+static int cont = 1 ;
+
+static inline void settimeout (int secs)
+{
+  tain_addsec_g(&deadline, secs) ;
+}
+
+static inline void settimeout_infinite (void)
+{
+  tain_add_g(&deadline, &tain_infinite_relative) ;
+}
+
+static inline void announce (void)
+{
+  if (!s6_svstatus_write(".", &status))
+    strerr_warnwu1sys("write status file") ;
+}
+
+
+/* The action array. */
+
+static void nop (void)
+{
+}
+
+static void bail (void)
+{
+  cont = 0 ;
+}
+
+static void killa (void)
+{
+  kill(status.pid, SIGALRM) ;
+}
+
+static void killb (void)
+{
+  kill(status.pid, SIGABRT) ;
+}
+
+static void killh (void)
+{
+  kill(status.pid, SIGHUP) ;
+}
+
+static void killq (void)
+{
+  kill(status.pid, SIGQUIT) ;
+}
+
+static void killk (void)
+{
+  kill(status.pid, SIGKILL) ;
+}
+
+static void killt (void)
+{
+  kill(status.pid, SIGTERM) ;
+}
+
+static void killi (void)
+{
+  kill(status.pid, SIGINT) ;
+}
+
+static void kill1 (void)
+{
+  kill(status.pid, SIGUSR1) ;
+}
+
+static void kill2 (void)
+{
+  kill(status.pid, SIGUSR2) ;
+}
+
+static void killp (void)
+{
+  kill(status.pid, SIGSTOP) ;
+  status.flagpaused = 1 ;
+  announce() ;
+}
+
+static void killc (void)
+{
+  kill(status.pid, SIGCONT) ;
+  status.flagpaused = 0 ;
+  announce() ;
+}
+
+static void trystart (void)
+{
+  int p[2] ;
+  pid_t pid ;
+  if (pipecoe(p) < 0)
+  {
+    settimeout(60) ;
+    strerr_warnwu1sys("pipecoe (waiting 60 seconds)") ;
+    return ;
+  }
+  pid = fork() ;
+  if (pid < 0)
+  {
+    settimeout(60) ;
+    strerr_warnwu1sys("fork (waiting 60 seconds)") ;
+    fd_close(p[1]) ; fd_close(p[0]) ;
+    return ;
+  }
+  else if (!pid)
+  {
+    char const *cargv[2] = { "run", 0 } ;
+    PROG = "s6-supervise (child)" ;
+    selfpipe_finish() ;
+    fd_close(p[0]) ;
+    if (flagsetsid) setsid() ;
+    execve("./run", (char *const *)cargv, (char *const *)environ) ;
+    fd_write(p[1], "", 1) ;
+    strerr_dieexec(111, "run") ;
+  }
+  fd_close(p[1]) ;
+  {
+    char c ;
+    switch (fd_read(p[0], &c, 1))
+    {
+      case -1 :
+        fd_close(p[0]) ;
+        settimeout(60) ;
+        strerr_warnwu1sys("read pipe (waiting 60 seconds)") ;
+        kill(pid, SIGKILL) ;
+        return ;
+      case 1 :
+      {
+        fd_close(p[0]) ;
+        settimeout(10) ;
+        strerr_warnwu1x("spawn ./run - waiting 10 seconds") ;
+        return ;
+      }
+    }
+  }
+  fd_close(p[0]) ;
+  settimeout_infinite() ;
+  state = UP ;
+  status.pid = pid ;
+  tain_copynow(&status.stamp) ;
+  announce() ;
+  ftrigw_notify(S6_SUPERVISE_EVENTDIR, 'u') ;
+}
+
+static void downtimeout (void)
+{
+  if (status.flagwant && status.flagwantup) trystart() ;
+  else settimeout_infinite() ;
+}
+
+static void down_O (void)
+{
+  status.flagwant = 0 ;
+  announce() ;
+}
+
+static void down_o (void)
+{
+  down_O() ;
+  trystart() ;
+}
+
+static void down_u (void)
+{
+  status.flagwant = 1 ;
+  status.flagwantup = 1 ;
+  announce() ;
+  trystart() ;
+}
+
+static void down_d (void)
+{
+  status.flagwant = 1 ;
+  status.flagwantup = 0 ;
+  announce() ;
+}
+
+static void tryfinish (int wstat, int islast)
+{
+  register pid_t pid = fork() ;
+  if (pid < 0)
+  {
+    strerr_warnwu2sys("fork for ", "./finish") ;
+    if (islast) bail() ;
+    state = DOWN ;
+    status.pid = 0 ;
+    settimeout(1) ;
+    return ;
+  }
+  else if (!pid)
+  {
+    char fmt0[UINT_FMT] ;
+    char fmt1[UINT_FMT] ;
+    char *cargv[4] = { "finish", fmt0, fmt1, 0 } ;
+    selfpipe_finish() ;
+    fmt0[uint_fmt(fmt0, WIFSIGNALED(wstat) ? 255 : WEXITSTATUS(wstat))] = 0 ;
+    fmt1[uint_fmt(fmt1, WIFSIGNALED(wstat))] = 0 ;
+    if (flagsetsid) setsid() ;
+    execve("./finish", cargv, (char *const *)environ) ;
+    _exit(111) ;
+  }
+  status.pid = pid ;
+  status.flagfinishing = 1 ;
+  state = islast ? LASTFINISH : FINISH ;
+  settimeout(5) ;
+}
+
+static void uptimeout (void)
+{
+  settimeout_infinite() ;
+  strerr_warnw1x("can't happen: timeout while the service is up!") ;
+}
+
+static void up_z (void)
+{
+  int wstat = status.pid ;
+  status.pid = 0 ;
+  tain_copynow(&status.stamp) ;
+  announce() ;
+  ftrigw_notify(S6_SUPERVISE_EVENTDIR, 'd') ;
+  tryfinish(wstat, 0) ;
+}
+
+static void up_o (void)
+{
+  status.flagwant = 0 ;
+  announce() ;
+}
+
+static void up_d (void)
+{
+  status.flagwant = 1 ;
+  status.flagwantup = 0 ;
+  killt() ;
+  killc() ;
+}
+
+static void up_u (void)
+{
+  status.flagwant = 1 ;
+  status.flagwantup = 1 ;
+  announce() ;
+}
+
+static void closethem (void)
+{
+  fd_close(0) ;
+  fd_close(1) ;
+  open_read("/dev/null") ;
+  open_write("/dev/null") ;
+}
+
+static void up_x (void)
+{
+  state = LASTUP ;
+  closethem() ;
+}
+
+static void up_term (void)
+{
+  up_x() ;
+  up_d() ;
+}
+
+static void finishtimeout (void)
+{
+  strerr_warnw1x("finish script takes too long - killing it") ;
+  killc() ; killk() ;
+  settimeout(3) ;
+}
+
+static void finish_z (void)
+{
+  status.pid = 0 ;
+  status.flagfinishing = 0 ;
+  state = DOWN ;
+  announce() ;
+  settimeout(1) ;
+}
+
+static void finish_u (void)
+{
+  status.flagwant = 1 ;
+  status.flagwantup = 1 ;
+  announce() ;
+}
+
+static void finish_x (void)
+{
+  state = LASTFINISH ;
+  closethem() ;
+}
+
+static void lastup_z (void)
+{
+  int wstat = status.pid ;
+  status.pid = 0 ;
+  tain_copynow(&status.stamp) ;
+  announce() ;
+  ftrigw_notify(S6_SUPERVISE_EVENTDIR, 'd') ;
+  tryfinish(wstat, 1) ;
+}
+
+static action_t_ref const actions[5][23] =
+{
+  { &downtimeout, &nop, &bail, &bail, &bail,
+    &nop, &nop, &nop, &nop, &nop, &nop, &nop, &nop, &nop, &nop, &nop, &nop, &nop,
+    &down_o, &down_d, &down_u, &bail, &down_O },
+  { &uptimeout, &up_z, &up_term, &up_x, &up_term,
+    &killa, &killb, &killq, &killh, &killk, &killt, &killi, &kill1, &kill2, &nop, &nop, &killp, &killc,
+    &up_o, &up_d, &up_u, &up_x, &up_o },
+  { &finishtimeout, &finish_z, &finish_x, &finish_x, &finish_x,
+    &nop, &nop, &nop, &nop, &nop, &nop, &nop, &nop, &nop, &nop, &nop, &nop, &nop,
+    &up_o, &down_d, &finish_u, &finish_x, &up_o },
+  { &uptimeout, &lastup_z, &up_d, &nop, &up_d,
+    &killa, &killb, &killq, &killh, &killk, &killt, &killi, &kill1, &kill2, &nop, &nop, &killp, &killc,
+    &up_o, &up_d, &nop, &nop, &up_o },
+  { &finishtimeout, &bail, &nop, &nop, &nop,
+    &nop, &nop, &nop, &nop, &nop, &nop, &nop, &nop, &nop, &nop, &nop, &nop, &nop,
+    &nop, &nop, &nop, &nop, &nop }
+} ;
+
+
+/* The main loop.
+   It just loops around the iopause(), calling snippets of code in "actions" when needed. */
+
+
+static void handle_signals (void)
+{
+  for (;;)
+  {
+    char c = selfpipe_read() ;
+    switch (c)
+    {
+      case -1 : strerr_diefu1sys(111, "selfpipe_read") ;
+      case 0 : return ;
+      case SIGCHLD :
+        if (!status.pid) wait_reap() ;
+        else
+        {
+          int wstat ;
+          int r = wait_pid_nohang(status.pid, &wstat) ;
+          if (r < 0)
+            if (errno != ECHILD) strerr_diefu1sys(111, "wait_pid_nohang") ;
+            else break ;
+          else if (!r) break ;
+          status.pid = wstat ;
+          (*actions[state][V_CHLD])() ;
+        }
+        break ;
+      case SIGTERM :
+        (*actions[state][V_TERM])() ;
+        break ;
+      case SIGHUP :
+        (*actions[state][V_HUP])() ;
+        break ;
+      case SIGQUIT :
+        (*actions[state][V_QUIT])() ;
+        break ;
+      default :
+        strerr_dief1x(101, "internal error: inconsistent signal state. Please submit a bug-report.") ;
+    }
+  }
+}
+
+static void handle_control (int fd)
+{
+  for (;;)
+  {
+    char c ;
+    register int r = sanitize_read(fd_read(fd, &c, 1)) ;
+    if (r < 0) strerr_diefu1sys(111, "read " S6_SUPERVISE_CTLDIR "/control") ;
+    else if (!r) break ;
+    else
+    {
+      register unsigned int pos = byte_chr("abqhkti12fFpcoduxO", 18, c) ;
+      if (pos < 18) (*actions[state][V_a + pos])() ;
+    }
+  }
+}
+
+int main (int argc, char const *const *argv)
+{
+  iopause_fd x[2] = { { -1, IOPAUSE_READ, 0 }, { -1, IOPAUSE_READ, 0 } } ;
+  PROG = "s6-supervise" ;
+  if (argc < 2) strerr_dieusage(100, USAGE) ;
+  if (chdir(argv[1]) < 0) strerr_diefu2sys(111, "chdir to ", argv[1]) ;
+  {
+    register unsigned int proglen = str_len(PROG) ;
+    register unsigned int namelen = str_len(argv[1]) ;
+    char progname[proglen + namelen + 2] ;
+    byte_copy(progname, proglen, PROG) ;
+    progname[proglen] = ' ' ;
+    byte_copy(progname + proglen + 1, namelen + 1, argv[1]) ;
+    PROG = progname ;
+    if (!fd_sanitize()) strerr_diefu1sys(111, "sanitize stdin and stdout") ;
+    x[1].fd = s6_supervise_lock(S6_SUPERVISE_CTLDIR) ;
+    if (!ftrigw_fifodir_make(S6_SUPERVISE_EVENTDIR, -1, 0))
+      strerr_diefu2sys(111, "mkfifodir ", S6_SUPERVISE_EVENTDIR) ;
+    x[0].fd = selfpipe_init() ;
+    if (x[0].fd == -1) strerr_diefu1sys(111, "init selfpipe") ;
+    if (sig_ignore(SIGPIPE) < 0) strerr_diefu1sys(111, "ignore SIGPIPE") ;
+    {
+      sigset_t set ;
+      sigemptyset(&set) ;
+      sigaddset(&set, SIGTERM) ;
+      sigaddset(&set, SIGHUP) ;
+      sigaddset(&set, SIGQUIT) ;
+      sigaddset(&set, SIGCHLD) ;
+      if (selfpipe_trapset(&set) < 0) strerr_diefu1sys(111, "trap signals") ;
+    }
+    
+    if (!ftrigw_clean(S6_SUPERVISE_EVENTDIR))
+      strerr_warnwu2sys("ftrigw_clean ", S6_SUPERVISE_EVENTDIR) ;
+
+    {
+      struct stat st ;
+      if (stat("down", &st) == -1)
+      {
+        if (errno != ENOENT)
+          strerr_diefu1sys(111, "stat down") ;
+      }
+      else status.flagwantup = 0 ;
+      if (stat("nosetsid", &st) == -1)
+      {
+        if (errno != ENOENT)
+          strerr_diefu1sys(111, "stat nosetsid") ;
+      }
+      else flagsetsid = 0 ;
+    }
+
+    tain_now_g() ;
+    settimeout(0) ;
+    tain_copynow(&status.stamp) ;
+    announce() ;
+    ftrigw_notify(S6_SUPERVISE_EVENTDIR, 's') ;
+
+    while (cont)
+    {
+      register int r = iopause_g(x, 2, &deadline) ;
+      if (r < 0) strerr_diefu1sys(111, "iopause") ;
+      else if (!r) (*actions[state][V_TIMEOUT])() ;
+      else
+      {
+        if ((x[0].revents | x[1].revents) & IOPAUSE_EXCEPT)
+          strerr_diefu1x(111, "iopause: trouble with pipes") ;
+        if (x[0].revents & IOPAUSE_READ) handle_signals() ;
+        else if (x[1].revents & IOPAUSE_READ) handle_control(x[1].fd) ;
+      }
+    }
+
+    ftrigw_notify(S6_SUPERVISE_EVENTDIR, 'x') ;
+  }
+  return 0 ;
+}
diff --git a/src/supervision/s6-svc.c b/src/supervision/s6-svc.c
new file mode 100644
index 0000000..699eefd
--- /dev/null
+++ b/src/supervision/s6-svc.c
@@ -0,0 +1,12 @@
+/* ISC license. */
+
+#include <skalibs/strerr2.h>
+#include <s6/s6-supervise.h>
+
+#define USAGE "s6-svc [ -abqhkti12fFpcoduxO ] servicedir"
+
+int main (int argc, char const *const *argv)
+{
+  PROG = "s6-svc" ;
+  return s6_svc_main(argc, argv, "abqhkti12fFpcoduxO", USAGE, "supervise") ;
+}
diff --git a/src/supervision/s6-svok.c b/src/supervision/s6-svok.c
new file mode 100644
index 0000000..4a615e9
--- /dev/null
+++ b/src/supervision/s6-svok.c
@@ -0,0 +1,32 @@
+/* ISC license. */
+
+#include <errno.h>
+#include <skalibs/bytestr.h>
+#include <skalibs/strerr2.h>
+#include <skalibs/djbunix.h>
+#include <s6/s6-supervise.h>
+
+#define USAGE "s6-svok servicedir"
+
+int main (int argc, char const *const *argv)
+{
+  PROG = "s6-svok" ;
+  if (argc < 2) strerr_dieusage(100, USAGE) ;
+  argv++ ; argc-- ;
+  {
+    int fd ;
+    unsigned int dirlen = str_len(*argv) ;
+    char fn[dirlen + 9 + sizeof(S6_SUPERVISE_CTLDIR)] ;
+    byte_copy(fn, dirlen, *argv) ;
+    fn[dirlen] = '/' ;
+    byte_copy(fn + dirlen + 1, sizeof(S6_SUPERVISE_CTLDIR) - 1, S6_SUPERVISE_CTLDIR) ;
+    byte_copy(fn + dirlen + sizeof(S6_SUPERVISE_CTLDIR), 9, "/control") ;
+    fd = open_write(fn) ;
+    if (fd < 0)
+    {
+      if ((errno == ENXIO) || (errno == ENOENT)) return 1 ;
+      else strerr_diefu2sys(111, "open_write ", fn) ;
+    }
+  }
+  return 0 ;
+}
diff --git a/src/supervision/s6-svscan.c b/src/supervision/s6-svscan.c
new file mode 100644
index 0000000..8b0f82e
--- /dev/null
+++ b/src/supervision/s6-svscan.c
@@ -0,0 +1,498 @@
+/* ISC license. */
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/wait.h>
+#include <unistd.h>
+#include <errno.h>
+#include <signal.h>
+#include <skalibs/allreadwrite.h>
+#include <skalibs/bytestr.h>
+#include <skalibs/sgetopt.h>
+#include <skalibs/uint.h>
+#include <skalibs/strerr2.h>
+#include <skalibs/tai.h>
+#include <skalibs/iopause.h>
+#include <skalibs/djbunix.h>
+#include <skalibs/direntry.h>
+#include <skalibs/sig.h>
+#include <skalibs/selfpipe.h>
+#include <skalibs/environ.h>
+#include <s6/config.h>
+#include <s6/s6-supervise.h>
+
+#define USAGE "s6-svscan [ -c maxservices ] [ -t timeout ] [ dir ]"
+
+#define FINISH_PROG S6_SVSCAN_CTLDIR "/finish"
+#define CRASH_PROG S6_SVSCAN_CTLDIR "/crash"
+
+#define DIR_RETRY_TIMEOUT 3
+#define CHECK_RETRY_TIMEOUT 4
+
+struct svinfo
+{
+  dev_t dev ;
+  ino_t ino ;
+  tain_t restartafter[2] ;
+  int pid[2] ;
+  int p[2] ;
+  unsigned int flagactive : 1 ;
+  unsigned int flaglog : 1 ;
+} ;
+#define SVINFO_ZERO { -1, -1, { TAIN_ZERO, TAIN_ZERO }, { 0, 0 }, { -1, -1 }, 0, 0, 0 } ;
+
+static struct svinfo *services ;
+static unsigned int max = 500 ;
+static unsigned int n = 0 ;
+static tain_t deadline, defaulttimeout ;
+static char const *finish_arg = "reboot" ;
+static int wantreap = 1 ;
+static int wantscan = 1 ;
+static unsigned int wantkill = 0 ;
+static int cont = 1 ;
+
+static void panicnosp (char const *) gccattr_noreturn ;
+static void panicnosp (char const *errmsg)
+{
+  char const *eargv[2] = { CRASH_PROG, 0 } ;
+  strerr_warnwu1sys(errmsg) ;
+  strerr_warnw2x("executing into ", eargv[0]) ;
+  execve(eargv[0], (char *const *)eargv, (char *const *)environ) ;
+ /* and if that execve fails, screw it and just die */
+  strerr_dieexec(111, eargv[0]) ;
+}
+
+static void panic (char const *) gccattr_noreturn ;
+static void panic (char const *errmsg)
+{
+  int e = errno ;
+  selfpipe_finish() ;
+  errno = e ;
+  panicnosp(errmsg) ;
+}
+
+static void killthem (void)
+{
+  register unsigned int i = 0 ;
+  if (!wantkill) return ;
+  for (; i < n ; i++)
+  {
+    if (!(wantkill & 1) && services[i].flagactive) continue ;
+    if (services[i].pid[0])
+      kill(services[i].pid[0], (wantkill & 2) ? SIGTERM : SIGHUP) ;
+    if (services[i].flaglog && services[i].pid[1])
+      kill(services[i].pid[1], (wantkill & 4) ? SIGTERM : SIGHUP) ;
+  }
+  wantkill = 0 ;
+}
+
+static void term (void)
+{
+  cont = 0 ;
+  wantkill = 3 ;
+}
+
+static void hup (void)
+{
+  cont = 0 ;
+  wantkill = 1 ;
+}
+
+static void quit (void)
+{
+  cont = 0 ;
+  wantkill = 7 ;
+}
+
+static void intr (void)
+{
+  finish_arg = "reboot" ;
+  term() ;
+}
+
+static void handle_signals (void)
+{
+  for (;;)
+  {
+    switch (selfpipe_read())
+    {
+      case -1 : panic("selfpipe_read") ;
+      case 0 : return ;
+      case SIGCHLD : wantreap = 1 ; break ;
+      case SIGALRM : wantscan = 1 ; break ;
+      case SIGTERM : term() ; break ;
+      case SIGHUP : hup() ; break ;
+      case SIGQUIT : quit() ; break ;
+      case SIGABRT : cont = 0 ; break ;
+      case SIGINT : intr() ; break ;
+    }
+  }
+}
+
+static void handle_control (int fd)
+{
+  for (;;)
+  {
+    char c ;
+    int r = sanitize_read(fd_read(fd, &c, 1)) ;
+    if (r == -1) panic("read control pipe") ;
+    else if (!r) break ;
+    else switch (c)
+    {
+      case 'p' : finish_arg = "poweroff" ; break ;
+      case 'h' : hup() ; return ;
+      case 'r' : finish_arg = "reboot" ; break ;
+      case 'a' : wantscan = 1 ; break ;
+      case 't' : term() ; return ;
+      case 's' : finish_arg = "halt" ; break ;
+      case 'z' : wantreap = 1 ; break ;
+      case 'b' : cont = 0 ; return ;
+      case 'n' : wantkill = 2 ; break ;
+      case 'N' : wantkill = 6 ; break ;
+      case '6' :
+      case 'i' : intr() ; return ;
+      case 'q' : quit() ; return ;
+      case '0' : finish_arg = "halt" ; term() ; return ;
+      case '7' : finish_arg = "poweroff" ; term() ; return ;
+      case '8' : finish_arg = "other" ; term() ; return ;
+      default :
+      {
+        char s[2] = { c, 0 } ;
+        strerr_warnw2x("received unknown control command: ", s) ;
+      }
+    }
+  }
+}
+
+
+/* First essential function: the reaper.
+   s6-svscan must wait() for all children,
+   including ones it doesn't know it has.
+   Dead active services are flagged to be restarted in 1 second. */
+
+static void reap (void)
+{
+  tain_t nextscan ;
+  if (!wantreap) return ;
+  wantreap = 0 ;
+  tain_addsec_g(&nextscan, 1) ;
+  for (;;)
+  {
+    int wstat ;
+    int r = wait_nohang(&wstat) ;
+    if (r < 0)
+      if (errno != ECHILD) panic("wait_nohang") ;
+      else break ;
+    else if (!r) break ;
+    else
+    {
+      register unsigned int i = 0 ;
+      for (; i < n ; i++)
+      {
+        if (services[i].pid[0] == r)
+        {
+          services[i].pid[0] = 0 ;
+          services[i].restartafter[0] = nextscan ;
+          break ;
+        }
+        else if (services[i].pid[1] == r)
+        {
+          services[i].pid[1] = 0 ;
+          services[i].restartafter[1] = nextscan ;
+          break ;
+        }
+      }
+      if (i == n) continue ;
+      if (services[i].flagactive)
+      {
+        if (tain_less(&nextscan, &deadline)) deadline = nextscan ;
+      }
+      else
+      {
+        if (services[i].flaglog)
+        {
+ /*
+    BLACK MAGIC:
+     - we need to close the pipe early:
+       * as soon as the writer exits so the logger can exit on EOF
+       * or as soon as the logger exits so the writer can crash on EPIPE
+     - but if the same service gets reactivated before the second
+       supervise process exits, ouch: we've lost the pipe
+     - so we can't reuse the same service even if it gets reactivated
+     - so we're marking a dying service with a closed pipe
+     - if the scanner sees a service with p[0] = -1 it won't flag
+       it as active (and won't restart the dead supervise)
+     - but if the service gets reactivated we want it to restart
+       as soon as the 2nd supervise process dies
+     - so the scanner marks such a process with p[0] = -2
+     - and the reaper triggers a scan when it finds a -2.
+ */
+          if (services[i].p[0] >= 0)
+          {
+            fd_close(services[i].p[1]) ; services[i].p[1] = -1 ;
+            fd_close(services[i].p[0]) ; services[i].p[0] = -1 ;
+          }
+          else if (services[i].p[0] == -2) wantscan = 1 ;
+        }
+        if (!services[i].pid[0] && !services[i].pid[1])
+          services[i] = services[--n] ;
+      }
+    }
+  }
+}
+
+
+/* Second essential function: the scanner.
+   It monitors the service directories and spawns a supervisor
+   if needed. */
+
+static void trystart (unsigned int i, char const *name, int islog)
+{
+  int pid = fork() ;
+  switch (pid)
+  {
+    case -1 :
+      tain_addsec_g(&services[i].restartafter[islog], CHECK_RETRY_TIMEOUT) ;
+      strerr_warnwu2sys("fork for ", name) ;
+      return ;
+    case 0 :
+    {
+      char const *cargv[3] = { "s6-supervise", name, 0 } ;
+      PROG = "s6-svscan (child)" ;
+      selfpipe_finish() ;
+      if (services[i].flaglog)
+        if (fd_move(!islog, services[i].p[!islog]) == -1)
+          strerr_diefu2sys(111, "set fds for ", name) ;
+      pathexec_run(S6_BINPREFIX "s6-supervise", cargv, (char const **)environ) ;
+      strerr_dieexec(111, S6_BINPREFIX "s6-supervise") ;
+    }
+  }
+  services[i].pid[islog] = pid ;
+}
+
+static void retrydirlater (void)
+{
+  tain_t a ;
+  tain_addsec_g(&a, DIR_RETRY_TIMEOUT) ;
+  if (tain_less(&a, &deadline)) deadline = a ;
+}
+
+static void check (char const *name)
+{
+  struct stat st ;
+  unsigned int namelen ;
+  unsigned int i = 0 ;
+  if (name[0] == '.') return ;
+  if (stat(name, &st) == -1)
+  {
+    strerr_warnwu2sys("stat ", name) ;
+    retrydirlater() ;
+    return ;
+  }
+  if (!S_ISDIR(st.st_mode)) return ;
+  namelen = str_len(name) ;
+  for (; i < n ; i++) if ((services[i].ino == st.st_ino) && (services[i].dev == st.st_dev)) break ;
+  if (i < n)
+  {
+    if (services[i].flaglog && (services[i].p[0] < 0))
+    {
+     /* See BLACK MAGIC above. */
+      services[i].p[0] = -2 ;
+      return ;
+    }
+  }
+  else
+  {
+    if (n >= max)
+    {
+      strerr_warnwu3x("start supervisor for ", name, ": too many services") ;
+      return ;
+    }
+    else
+    {
+      struct stat su ;
+      char tmp[namelen + 5] ;
+      byte_copy(tmp, namelen, name) ;
+      byte_copy(tmp + namelen, 5, "/log") ;
+      if (stat(tmp, &su) < 0)
+        if (errno == ENOENT) services[i].flaglog = 0 ;
+        else
+        {
+          strerr_warnwu2sys("stat ", tmp) ;
+          retrydirlater() ;
+          return ;
+        }
+      else if (!S_ISDIR(su.st_mode))
+        services[i].flaglog = 0 ;
+      else
+      {
+        if (pipecoe(services[i].p) < 0)
+        {
+          strerr_warnwu1sys("pipecoe") ;
+          retrydirlater() ;
+          return ;
+        }
+        services[i].flaglog = 1 ;
+      }
+      services[i].ino = st.st_ino ;
+      services[i].dev = st.st_dev ;
+      tain_copynow(&services[i].restartafter[0]) ;
+      tain_copynow(&services[i].restartafter[1]) ;
+      services[i].pid[0] = 0 ;
+      services[i].pid[1] = 0 ;
+      n++ ;
+    }
+  }
+  
+  services[i].flagactive = 1 ;
+
+  if (services[i].flaglog && !services[i].pid[1])
+  {
+    if (!tain_future(&services[i].restartafter[1]))
+    {
+      char tmp[namelen + 5] ;
+      byte_copy(tmp, namelen, name) ;
+      byte_copy(tmp + namelen, 5, "/log") ;
+      trystart(i, tmp, 1) ;
+    }
+    else if (tain_less(&services[i].restartafter[1], &deadline))
+      deadline = services[i].restartafter[1] ;
+  }
+
+  if (!services[i].pid[0])
+  {
+    if (!tain_future(&services[i].restartafter[0]))
+      trystart(i, name, 0) ;
+    else if (tain_less(&services[i].restartafter[0], &deadline))
+      deadline = services[i].restartafter[0] ;
+  }
+}
+
+static void scan (void)
+{
+  DIR *dir ;
+  if (!wantscan) return ;
+  wantscan = 0 ;
+  dir = opendir(".") ;
+  if (!dir)
+  {
+    strerr_warnwu1sys("opendir .") ;
+    retrydirlater() ;
+    return ;
+  }
+  {
+    register unsigned int i = 0 ;
+    for (; i < n ; i++) services[i].flagactive = 0 ;
+  }
+  for (;;)
+  {
+    direntry *d ;
+    errno = 0 ;
+    d = readdir(dir) ;
+    if (!d) break ;
+    check(d->d_name) ;
+  }
+  if (errno)
+  {
+    strerr_warnwu1sys("readdir .") ;
+    retrydirlater() ;
+  }
+  dir_close(dir) ;
+}
+
+
+int main (int argc, char const *const *argv)
+{
+  iopause_fd x[2] = { { -1, IOPAUSE_READ, 0 }, { -1, IOPAUSE_READ, 0 } } ;
+  PROG = "s6-svscan" ;
+  {
+    subgetopt_t l = SUBGETOPT_ZERO ;
+    unsigned int t = 5000 ;
+    for (;;)
+    {
+      register int opt = subgetopt_r(argc, argv, "t:c:", &l) ;
+      if (opt == -1) break ;
+      switch (opt)
+      {
+        case 't' : if (uint0_scan(l.arg, &t)) break ;
+        case 'c' : if (uint0_scan(l.arg, &max)) break ;
+        default : strerr_dieusage(100, USAGE) ;
+      }
+    }
+    argc -= l.ind ; argv += l.ind ;
+    if (t) tain_from_millisecs(&defaulttimeout, t) ;
+    else defaulttimeout = tain_infinite_relative ;
+    if (max < 2) max = 2 ;
+  }
+
+  /* Init phase.
+     If something fails here, we can die, because it means that
+     something is seriously wrong with the system, and we can't
+     run correctly anyway.
+  */
+
+  if (argc && (chdir(argv[0]) < 0)) strerr_diefu1sys(111, "chdir") ;
+  x[1].fd = s6_supervise_lock(S6_SVSCAN_CTLDIR) ;
+  x[0].fd = selfpipe_init() ;
+  if (x[0].fd < 0) strerr_diefu1sys(111, "selfpipe_init") ;
+
+  if (sig_ignore(SIGPIPE) < 0) strerr_diefu1sys(111, "ignore SIGPIPE") ;
+  {
+    sigset_t set ;
+    sigemptyset(&set) ;
+    sigaddset(&set, SIGCHLD) ;
+    sigaddset(&set, SIGALRM) ;
+    sigaddset(&set, SIGTERM) ;
+    sigaddset(&set, SIGHUP) ;
+    sigaddset(&set, SIGQUIT) ;
+    sigaddset(&set, SIGABRT) ;
+    sigaddset(&set, SIGINT) ;
+    if (selfpipe_trapset(&set) < 0) strerr_diefu1sys(111, "trap signals") ;
+  }
+
+
+  {
+    struct svinfo blob[max] ; /* careful with that stack, Eugene */
+    services = blob ;
+    tain_now_g() ;
+
+
+    /* Loop phase.
+       From now on, we must not die.
+       Temporize on recoverable errors, and panic on serious ones. */
+
+    while (cont)
+    {
+      int r ;
+      tain_add_g(&deadline, &defaulttimeout) ;
+      reap() ;
+      scan() ;
+      killthem() ;
+      r = iopause_g(x, 2, &deadline) ;
+      if (r < 0) panic("iopause") ;
+      else if (!r) wantscan = 1 ;
+      else
+      {
+        if ((x[0].revents | x[1].revents) & IOPAUSE_EXCEPT)
+        {
+          errno = EIO ;
+          panic("check internal pipes") ;
+        }
+        if (x[0].revents & IOPAUSE_READ) handle_signals() ;
+        if (x[1].revents & IOPAUSE_READ) handle_control(x[1].fd) ;
+      }
+    }
+
+
+    /* Finish phase. */
+
+    selfpipe_finish() ;
+    killthem() ;
+    reap() ;
+  }
+  {
+    char const *eargv[3] = { FINISH_PROG, finish_arg, 0 } ;
+    execve(eargv[0], (char **)eargv, (char *const *)environ) ;
+  }
+  panicnosp("exec finish script " FINISH_PROG) ;
+}
diff --git a/src/supervision/s6-svscanctl.c b/src/supervision/s6-svscanctl.c
new file mode 100644
index 0000000..48e6420
--- /dev/null
+++ b/src/supervision/s6-svscanctl.c
@@ -0,0 +1,12 @@
+/* ISC license. */
+
+#include <skalibs/strerr2.h>
+#include <s6/s6-supervise.h>
+
+#define USAGE "s6-svscanctl [ -phratszbnNiq0678 ] svscandir"
+
+int main (int argc, char const *const *argv)
+{
+  PROG = "s6-svscanctl" ;
+  return s6_svc_main(argc, argv, "phratszbnNiq0678", USAGE, ".s6-svscan") ;
+}
diff --git a/src/supervision/s6-svstat.c b/src/supervision/s6-svstat.c
new file mode 100644
index 0000000..c986b8d
--- /dev/null
+++ b/src/supervision/s6-svstat.c
@@ -0,0 +1,70 @@
+/* ISC license. */
+
+#include <errno.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <skalibs/uint64.h>
+#include <skalibs/uint.h>
+#include <skalibs/bytestr.h>
+#include <skalibs/buffer.h>
+#include <skalibs/strerr2.h>
+#include <skalibs/tai.h>
+#include <skalibs/djbunix.h>
+#include <s6/s6-supervise.h>
+
+#define USAGE "s6-svstat servicedir"
+
+int main (int argc, char const *const *argv)
+{
+  s6_svstatus_t status ;
+  char fmt[UINT_FMT] ;
+  int isup, normallyup ;
+  PROG = "s6-svstat" ;
+  if (argc < 2) strerr_dieusage(100, USAGE) ;
+  argv++ ; argc-- ;
+  if (!s6_svstatus_read(*argv, &status))
+    strerr_diefu2sys(111, "read status for ", *argv) ;
+
+  {
+    struct stat st ;
+    unsigned int dirlen = str_len(*argv) ;
+    char fn[dirlen + 6] ;
+    byte_copy(fn, dirlen, *argv) ;
+    byte_copy(fn + dirlen, 6, "/down") ;
+    if (stat(fn, &st) == -1)
+      if (errno != ENOENT) strerr_diefu2sys(111, "stat ", fn) ;
+      else normallyup = 1 ;
+    else normallyup = 0 ;
+  }
+
+  tain_now_g() ;
+  if (tain_future(&status.stamp)) tain_copynow(&status.stamp) ;
+  tain_sub(&status.stamp, &STAMP, &status.stamp) ;
+
+  isup = status.pid && !status.flagfinishing ;
+  if (isup)
+  {
+    buffer_putnoflush(buffer_1small,"up (pid ", 8) ;
+    buffer_putnoflush(buffer_1small, fmt, uint_fmt(fmt, status.pid)) ;
+    buffer_putnoflush(buffer_1small, ") ", 2) ;
+  }
+  else buffer_putnoflush(buffer_1small, "down ", 5) ;
+
+  buffer_putnoflush(buffer_1small, fmt, uint64_fmt(fmt, status.stamp.sec.x)) ;
+  buffer_putnoflush(buffer_1small," seconds", 8) ;
+
+  if (isup && !normallyup)
+    buffer_putnoflush(buffer_1small, ", normally down", 15) ;
+  if (!isup && normallyup)
+    buffer_putnoflush(buffer_1small, ", normally up", 13) ;
+  if (isup && status.flagpaused)
+    buffer_putnoflush(buffer_1small, ", paused", 8) ;
+  if (!isup && (status.flagwant == 'u'))
+    buffer_putnoflush(buffer_1small, ", want up", 10) ;
+  if (isup && (status.flagwant == 'd'))
+    buffer_putnoflush(buffer_1small, ", want down", 12) ;
+
+  if (buffer_putflush(buffer_1small, "\n", 1) < 0)
+    strerr_diefu1sys(111, "write to stdout") ;
+  return 0 ;
+}
diff --git a/src/supervision/s6-svwait.c b/src/supervision/s6-svwait.c
new file mode 100644
index 0000000..0d7c96c
--- /dev/null
+++ b/src/supervision/s6-svwait.c
@@ -0,0 +1,104 @@
+/* ISC license. */
+
+#include <skalibs/sgetopt.h>
+#include <skalibs/bytestr.h>
+#include <skalibs/uint16.h>
+#include <skalibs/uint.h>
+#include <skalibs/bitarray.h>
+#include <skalibs/tai.h>
+#include <skalibs/strerr2.h>
+#include <skalibs/iopause.h>
+#include <s6/ftrigr.h>
+#include <s6/s6-supervise.h>
+
+#define USAGE "s6-svwait [ -U | -u | -d ] [ -A | -a | -o ] [ -t timeout ] servicedir..."
+#define dieusage() strerr_dieusage(100, USAGE)
+
+static inline int check (unsigned char const *ba, unsigned int n, int wantup, int or)
+{
+  return (bitarray_first(ba, n, or == wantup) < n) == or ;
+}
+
+int main (int argc, char const *const *argv)
+{
+  tain_t deadline, tto ;
+  ftrigr_t a = FTRIGR_ZERO ;
+  uint32 options = FTRIGR_REPEAT ;
+  int or = 0 ;
+  int wantup = 1 ;
+  char re[4] = "u|d" ;
+  PROG = "s6-svwait" ;
+  {
+    subgetopt_t l = SUBGETOPT_ZERO ;
+    unsigned int t = 0 ;
+    for (;;)
+    {
+      register int opt = subgetopt_r(argc, argv, "uUdAaot:", &l) ;
+      if (opt == -1) break ;
+      switch (opt)
+      {
+        case 'U' : wantup = 1 ; re[0] = 'U' ; break ;
+        case 'u' : wantup = 1 ; re[0] = 'u' ; break ;
+        case 'd' : wantup = 0 ; break ;
+        case 'A' : or = 0 ; options |= FTRIGR_REPEAT ; break ;
+        case 'a' : or = 0 ; options &= ~FTRIGR_REPEAT ; break ;
+        case 'o' : or = 1 ; options &= ~FTRIGR_REPEAT ; break ;
+        case 't' : if (!uint0_scan(l.arg, &t)) dieusage() ; break ;
+        default : dieusage() ;
+      }
+    }
+    argc -= l.ind ; argv += l.ind ;
+    if (t) tain_from_millisecs(&tto, t) ; else tto = tain_infinite_relative ;
+  }
+  if (!argc) dieusage() ;
+
+  tain_now_g() ;
+  tain_add_g(&deadline, &tto) ;
+
+  if (!ftrigr_startf_g(&a, &deadline)) strerr_diefu1sys(111, "ftrigr_startf") ;
+
+  {
+    iopause_fd x = { -1, IOPAUSE_READ, 0 } ;
+    unsigned int i = 0 ;
+    uint16 list[argc] ;
+    unsigned char states[bitarray_div8(argc)] ;
+    x.fd = ftrigr_fd(&a) ;
+    for (; i < (unsigned int)argc ; i++)
+    {
+      unsigned int len = str_len(argv[i]) ;
+      char s[len + 1 + sizeof(S6_SUPERVISE_EVENTDIR)] ;
+      byte_copy(s, len, argv[i]) ;
+      s[len] = '/' ;
+      byte_copy(s + len + 1, sizeof(S6_SUPERVISE_EVENTDIR), S6_SUPERVISE_EVENTDIR) ;
+      list[i] = ftrigr_subscribe_g(&a, s, re, options, &deadline) ;
+      if (!list[i]) strerr_diefu2sys(111, "ftrigr_subscribe to ", argv[i]) ;
+    }
+
+    for (i = 0 ; i < (unsigned int)argc ; i++)
+    {
+      s6_svstatus_t st = S6_SVSTATUS_ZERO ;
+      if (!s6_svstatus_read(argv[i], &st)) strerr_diefu1sys(111, "s6_svstatus_read") ;
+      bitarray_poke(states, i, !!st.pid) ;
+    }
+
+    for (;;)
+    {
+      if (check(states, argc, wantup, or)) break ;
+      {
+        register int r = iopause_g(&x, 1, &deadline) ;
+        if (r < 0) strerr_diefu1sys(111, "iopause") ;
+        else if (!r) strerr_dief1x(1, "timed out") ;
+      }
+
+      if (ftrigr_update(&a) < 0) strerr_diefu1sys(111, "ftrigr_update") ;
+      for (i = 0 ; i < (unsigned int)argc ; i++)
+      {
+        char what ;
+        register int r = ftrigr_check(&a, list[i], &what) ;
+        if (r < 0) strerr_diefu1sys(111, "ftrigr_check") ;
+        if (r) bitarray_poke(states, i, what == re[0]) ;
+      } 
+    }
+  }
+  return 0 ;
+}