Add child_spawn3, make textclient_startf use it

4 files changed, 181 insertions, 6 deletions

diff --git a/src/include/skalibs/djbunix.h b/src/include/skalibs/djbunix.h
index 00d8f00..ebcba18 100644
--- a/src/include/skalibs/djbunix.h
+++ b/src/include/skalibs/djbunix.h
@@ -183,14 +183,24 @@ extern pid_t child_spawn2 (char const *, char const *const *, char const *const
 
 
  /*
-    Unified function to fork a child with communication channels (pipes).
+    Same, with an additional pipe from the child to the parent.
+    The int * points to 3 fds.
+    The additional fd# is available to the child in the defined env variable.
+ */
+
+#define SKALIBS_CHILD_SPAWN_FDS_ENVVAR "SKALIBS_CHILD_SPAWN_FDS"
+
+extern pid_t child_spawn3 (char const *, char const *const *, char const *const *, int *) ;
+
+
+ /*
+    Generalization of the previous functions.
     * uses posix_spawn() if available, else uses fork+exec
-    * requests n (the last arg) communication fds between parent and child
+    * requests n (the last arg) communication fds between parent and child. Uses pipes.
     * if n=1, equivalent to child_spawn1_pipe; child writes, parent reads.
     * if n>=2, parent reads on even and writes on odd.
  */
 
-#define SKALIBS_CHILD_SPAWN_FDS_ENVVAR "SKALIBS_CHILD_SPAWN_FDS"
 
 extern pid_t child_spawn (char const *, char const *const *, char const *const *, int *, unsigned int) ;
 
diff --git a/src/libstddjb/child_spawn.c b/src/libstddjb/child_spawn.c
index 82edf8a..964e4e2 100644
--- a/src/libstddjb/child_spawn.c
+++ b/src/libstddjb/child_spawn.c
@@ -95,7 +95,7 @@ pid_t child_spawn (char const *prog, char const *const *argv, char const *const
     int haspath = !!getenv("PATH") ;
     size_t envlen = env_len(envp) ;
     char const *newenv[envlen + 2] ;
-    if (!env_merge(newenv, envlen+2, envp, envlen, modifs, m)) goto errsp ;
+    if (!env_merge(newenv, envlen+2, envp, envlen, modifs, m)) goto erractions ;
     if (!haspath && (setenv("PATH", SKALIBS_DEFAULTPATH, 0) < 0))
     {
       e = errno ; goto erractions ;
diff --git a/src/libstddjb/child_spawn3.c b/src/libstddjb/child_spawn3.c
new file mode 100644
index 0000000..82220ea
--- /dev/null
+++ b/src/libstddjb/child_spawn3.c
@@ -0,0 +1,165 @@
+/* ISC license. */
+
+/* MT-unsafe */
+
+#include <skalibs/sysdeps.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <sys/wait.h>
+#include <unistd.h>
+#include <errno.h>
+#include <signal.h>
+
+#ifdef SKALIBS_HASPOSIXSPAWN
+
+#include <stdlib.h>
+#include <spawn.h>
+#include <skalibs/config.h>
+
+#else
+
+#include <string.h>
+#include <skalibs/sig.h>
+#include <skalibs/strerr2.h>
+
+#endif
+
+#include <skalibs/types.h>
+#include <skalibs/allreadwrite.h>
+#include <skalibs/env.h>
+#include <skalibs/djbunix.h>
+
+pid_t child_spawn3 (char const *prog, char const *const *argv, char const *const *envp, int *fds)
+{
+#ifdef SKALIBS_HASPOSIXSPAWN
+  posix_spawn_file_actions_t actions ;
+  posix_spawnattr_t attr ;
+#else
+  int syncpipe[2] ;
+#endif
+  int p[3][2] ;
+  pid_t pid ;
+  int e ;
+  size_t m = sizeof(SKALIBS_CHILD_SPAWN_FDS_ENVVAR) ;
+  char modifs[sizeof(SKALIBS_CHILD_SPAWN_FDS_ENVVAR) + UINT_FMT] = SKALIBS_CHILD_SPAWN_FDS_ENVVAR "=" ;
+  if (pipe(p[0]) < 0 || ndelay_on(p[0][0]) < 0 || coe(p[0][0]) < 0) return 0 ;
+  if (pipe(p[1]) < 0 || ndelay_on(p[1][1]) < 0 || coe(p[1][1]) < 0) goto errp0 ;
+  if (pipe(p[2]) < 0 || ndelay_on(p[2][0]) < 0 || coe(p[2][0]) < 0) goto errp1 ;
+  m += uint_fmt(modifs + sizeof(SKALIBS_CHILD_SPAWN_FDS_ENVVAR), p[2][1]) ;
+  modifs[m++] = 0 ;
+
+#ifdef SKALIBS_HASPOSIXSPAWN
+
+  e = posix_spawnattr_init(&attr) ;
+  if (e) goto errp2 ;
+  {
+    sigset_t set ;
+    sigemptyset(&set) ;
+    e = posix_spawnattr_setsigmask(&attr, &set) ;
+    if (e) goto errattr ;
+    e = posix_spawnattr_setflags(&attr, POSIX_SPAWN_SETSIGMASK) ;
+    if (e) goto errattr ;
+  }
+  e = posix_spawn_file_actions_init(&actions) ;
+  if (e) goto errattr ;
+  e = posix_spawn_file_actions_adddup2(&actions, p[1][0], fds[0]) ;
+  if (e) goto erractions ;
+  e = posix_spawn_file_actions_addclose(&actions, p[1][0]) ;
+  if (e) goto erractions ;
+  e = posix_spawn_file_actions_adddup2(&actions, p[0][1], fds[1]) ;
+  if (e) goto erractions ;
+  e = posix_spawn_file_actions_addclose(&actions, p[0][1]) ;
+  if (e) goto erractions ;
+  {
+    int haspath = !!getenv("PATH") ;
+    size_t envlen = env_len(envp) ;
+    char const *newenv[envlen + 2] ;
+    if (!env_merge(newenv, envlen+2, envp, envlen, modifs, m)) goto erractions ;
+    if (!haspath && (setenv("PATH", SKALIBS_DEFAULTPATH, 0) < 0))
+    {
+      e = errno ; goto erractions ;
+    }
+    e = posix_spawnp(&pid, prog, &actions, &attr, (char *const *)argv, (char *const *)newenv) ;
+    if (!haspath) unsetenv("PATH") ;
+    if (e) goto erractions ;
+  }
+
+  posix_spawn_file_actions_destroy(&actions) ;
+  posix_spawnattr_destroy(&attr) ;
+
+#else
+  if (pipe(syncpipe) < 0) { e = errno ; goto errp2 ; }
+  if (coe(syncpipe[1]) < 0) { e = errno ; goto errsp ; }
+
+  pid = fork() ;
+  if (pid < 0) { e = errno ; goto errsp ; }
+  else if (!pid)
+  {
+    size_t len = strlen(PROG) ;
+    char name[len + 9] ;
+    memcpy(name, PROG, len) ;
+    memcpy(name + len, " (child)", 9) ;
+    PROG = name ;
+    fd_close(syncpipe[0]) ;
+    if (fd_move2(fds[0], p[1][0], fds[1], p[0][1]) < 0) goto syncdie ;
+    sig_blocknone() ;
+    pathexec_r_name(prog, argv, envp, env_len(envp), modifs, m) ;
+
+  syncdie:
+    {
+      char c = errno ;
+      fd_write(syncpipe[1], &c, 1) ;
+    }
+    _exit(127) ;
+  }
+
+  fd_close(syncpipe[1]) ;
+  {
+    char c ;
+    syncpipe[1] = fd_read(syncpipe[0], &c, 1) ;
+    if (syncpipe[1])
+    {
+      if (syncpipe[1] < 0) e = errno ;
+      else
+      {
+        kill(pid, SIGKILL) ;
+        e = c ;
+      }
+      wait_pid(pid, &syncpipe[1]) ;
+      goto errsp0 ;
+    }
+  }
+  fd_close(syncpipe[0]) ;
+#endif
+
+  fd_close(p[2][1]) ;
+  fd_close(p[1][0]) ;
+  fd_close(p[0][1]) ;
+  fds[0] = p[0][0] ;
+  fds[1] = p[1][1] ;
+  fds[2] = p[2][0] ;
+  return pid ;
+
+#ifdef SKALIBS_HASPOSIXSPAWN
+ erractions:
+  posix_spawn_file_actions_destroy(&actions) ;
+ errattr:
+  posix_spawnattr_destroy(&attr) ;
+#endif
+#ifndef SKALIBS_HASPOSIXSPAWN
+ errsp:
+  fd_close(syncpipe[1]) ;
+ errsp0:
+  fd_close(syncpipe[0]) ;
+#endif
+ errp2:
+  fd_close(p[2][1]) ;
+  fd_close(p[2][0]) ;
+ errp1:
+  fd_close(p[1][1]) ;
+  fd_close(p[1][0]) ;
+ errp0:
+  fd_close(p[0][1]) ;
+  fd_close(p[0][0]) ;
+  return 0 ;
+}
diff --git a/src/libunixonacid/textclient_startf.c b/src/libunixonacid/textclient_startf.c
index fd724cd..6a6f0fc 100644
--- a/src/libunixonacid/textclient_startf.c
+++ b/src/libunixonacid/textclient_startf.c
@@ -12,8 +12,8 @@
 int textclient_startf (textclient_t *a, char const *const *argv, char const *const *envp, uint32_t options, char const *before, size_t beforelen, char const *after, size_t afterlen, tain_t const *deadline, tain_t *stamp)
 {
   struct iovec v ;
-  int fd[3] ;
-  pid_t pid = child_spawn(argv[0], argv, envp, fd, 3) ;
+  int fd[3] = { 0, 1 } ;
+  pid_t pid = child_spawn3(argv[0], argv, envp, fd) ;
   if (!pid) return 0 ;
   textmessage_receiver_init(&a->syncin, fd[0], a->syncbuf, TEXTCLIENT_BUFSIZE, TEXTMESSAGE_MAXLEN) ;
   textmessage_receiver_init(&a->asyncin, fd[2], a->asyncbuf, TEXTCLIENT_BUFSIZE, TEXTMESSAGE_MAXLEN) ;