prefork-interp: wip

[chiark-utils.git] / prefork-interp.c

diff --git a/prefork-interp.c b/prefork-interp.c
index f37c8fdcb367f1b39993976109b9874b338a2f68..07e9fb0dd94eb4ee32cbac996b92fc27aff938fc 100644 (file)
--- a/prefork-interp.c
+++ b/prefork-interp.c
@@ -53,7 +53,7 @@
  *
  *        [server (script)]   accepts, forks monitor
  *
- *          monitor           [fd[012]: null]
+ *          monitor [1]       [fd[012]: null]
  *                            other fds: syslog, call(server-end)
  *                            sends ack byte
  *                            receives args, env, fds
@@ -62,7 +62,7 @@
  *            executor        sorts out fds:
  *                            fd0, fd1, fd2: from-outer-caller
  *                            close fds: call(server-end)
- *                            implicitly closed fds: syslog
+ *                            retained fds: syslog
  *
  *                            sets cmdline, env
  *                            runs main part of script
@@ -128,9 +128,122 @@ static void propagate_exit_status(int status, const char *what) {
   die("setup failed with weird wait status %d 0x%x", status, status);
 }
 
+static void die_data_overflow __attribute((noreturn)) {
+  die("cannot handle data with length >2^32");
+}
+
+static void prepare_data(size_t *len, char **buf,
+                        const void *data, size_t dl) {
+  if (len) {
+    if (dl >= SIZE_MAX - *len)
+      die_data_overlow();
+    *len += dl;
+  }
+  if (buf) {
+    memcpy(*buf, data, dl);
+    *buf += dl;
+  }
+}
+  
+static void prepare_length(size_t *len, char **buf, size_t dl) {
+  if (dl > UINT32_MAX) die_data_overflow();
+  uint32_t dl = htonl(dl);
+  prepare_data(len, buf, &dl, sizeof(dl));
+}
+
+static void prepare_string(size_t *len, char **buf, const char *string) {
+  size_t sl = strlen(s);
+  prepare_data(len, buf, s, sl+1);
+}
+
+static void prepare_message(size_t *len, char **buf,
+                           const char *const *argv) {
+  const char *s;
+
+  const char *const *p = environ;
+  while ((s = *p++)) {
+    if (strchr(s, '='))
+      prepare_string(len, buf, s);
+  }
+
+  prepare_string(len, buf, "");
+
+  p = argv;
+  while ((s = *p++))
+    prepare_string(len, buf, s);
+}
+
+static void send_fd(int via_fd, int payload_fd) {
+  union {
+    struct cmsghdr align;
+    char buf[CMSG_SPACE(sizeof(payload_fd))];
+  } msg;
+  struct msghdr msg;
+  FILLZERO(msg);
+
+  struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msg);
+  cmsg->cmsg_level = SOL_SOCKET;
+  cmsg->cmsg_type = SCM_RIGHTS;
+  cmsg->cmsg_len = CMSG_LEN(sizeof(payload_fd));
+  *(int*)CMSG_DATA(cmsg) = payload_fd;
+
+  char dummy_byte = 0;
+
+  struct iovec iov;
+  FIULLZERO(iov);
+  iov.iov_base = &dummy_byte;
+  iov.iov_len = 1;
+
+  msg.msg_name = 0;
+  msg.msg_iov = &iov;
+  msg.msg_iovlen = 1;
+  msg.msg_control = msg.buf;
+  msg.msg_controllen = sizeof(msg.buf);
+
+  for (;;) {
+    ssize_t r = sendmsg(via_fd, &msg, 0);
+    if (r == -1) {
+      if (errno == EINTR) continue;
+      diee("send fd");
+    }
+    assert!(r == 1);
+    break;
+  }
+}
+
+static void send_request(int call_fd, const char *const *argv) {
+  // Sending these first makes it easier for the script to
+  // use buffered IO for the message.
+  send_fd(call_fd, 0);
+  send_fd(call_fd, 1);
+  send_fd(call_fd, 2);
+
+  size_t len = 4;
+  prepare_message(&len, 0, argv);
+  char *m = malloc(len);
+  if (!m) diee("failed to allocate for message");
+  char *p = m;
+  prepare_length(0, &p, len - 4);
+  prepare_message(0, &p, argv);
+  assert(p == m + len);
+
+  p = m;
+  while (len) {
+    ssize_t r = write(call_fd, p, len);
+    if (r==-1) {
+      if (errno == EINTR) continue;
+      diee("write request");
+    }
+    assert(r <= len);
+    assert(r > 0);
+    len -= r;
+    p += r;
+  }
+}
+
 // Returns: call(client-end) fd, or -1 to mean "is garbage"
 // find_socket_path must have been called
-static int attempt_connect_existing(void) {
+static int connect_existing(void) {
   int r;
   int fd = -1;
 
@@ -157,9 +270,14 @@ static int attempt_connect_existing(void) {
     }
     if (sr == 0) { goto x_garbage; }
     if (ack != '\n') die("got ack byte 0x%02x, not '\n'", ack);
-    return fd;
+    break;
   }
 
+  // We're committed now, send the request (or bail out)
+  send_request(call, argv);
+
+  return fd;
+
  x_garbage:
   if (fd >= 0) close(fd);
   return -1;