libipm: Add support for sending file descriptors

libipm/libipm.c

@@ -32,6 +32,35 @@
 
 const char *libipm_valid_type_chars = "ybnqiuxtsdhogB";
 
+/**************************************************************************//**
+ * Send function for a struct trans initialised with libipm_init_trans()
+ *
+ * @param trans Transport to send on
+ * @param data pointer to data to send
+ * @param len Length of data to send
+ * @return As for write(2)
+ */
+static int
+libipm_trans_send_proc(struct trans *self, const char *data, int len)
+{
+    int rv;
+    struct libipm_priv *priv = (struct libipm_priv *)self->extra_data;
+    if (priv != NULL && data == self->out_s->data)
+    {
+        /* We're sending the message header. Send any file descriptors
+         * as ancillary data */
+        rv = g_sck_send_fd_set(self->sck, data, len,
+                               priv->out_fds, priv->out_fd_count);
+    }
+    else
+    {
+        rv = g_sck_send(self->sck, data, len, 0);
+    }
+
+    return rv;
+}
+
+
 /**************************************************************************//**
  * Destructor for a struct trans initialised with libipm_init_trans()
  *
@@ -83,6 +112,7 @@ libipm_init_trans(struct trans *trans,
         priv->facility = facility;
         priv->msgno_to_str = msgno_to_str;
 
+        trans->trans_send = libipm_trans_send_proc;
         trans->extra_data = priv;
         trans->extra_destructor = libipm_trans_destructor;
 

libipm/libipm.h

@@ -67,6 +67,7 @@ enum libipm_status
     E_LI_UNIMPLEMENTED_TYPE, /***< Specified type code is unimplemented */
     E_LI_UNEXPECTED_TYPE, /***< Encountered unexpected type on input */
     E_LI_BUFFER_OVERFLOW, /***< End of buffer reached unexpectedly */
+    E_LI_TOO_MANY_FDS, /***< Too many file descriptors encountered */
     E_LI_BAD_VALUE, /***< Specified (or incoming) value is out of range */
     E_LI_BAD_HEADER, /***< Bad incoming message header */
     E_LI_TRANSPORT_ERROR /***< Error detected at the transport level */
@@ -154,14 +155,17 @@ libipm_msg_out_init(struct trans *trans, unsigned short msgno,
  *   x  |int64_t  | Signed (two's complement) 64-bit integer
  *   t  |uint64_t | Unsigned 64-bit integer
  *   s  |char *   | NULL-terminated string
+ *   h  |int      | File descriptor
  *   d  |  -      | (reserved)
- *   h  |  -      | (reserved)
  *   o  |  -      | (reserved)
  *   g  |  -      | (reserved)
  *
  * For the 'b' type, only values 0 and 1 are allowed. Other values
  * generate an error.
  *
+ * The 'h' type can only be used where the underlying transport is a
+ * UNIX domain socket.
+ *
  *  The following additions to the D-Bus type system are also supported:-
  *
  * Char |C Type                    | Description

libipm/libipm_private.h

@@ -39,7 +39,12 @@ enum
     /**
      * Size of libipm header
      */
-    HEADER_SIZE = 12
+    HEADER_SIZE = 12,
+
+    /**
+     * Max number of file descriptors in a message
+     */
+    MAX_FD_PER_MSG = 8
 };
 
 /**
@@ -52,6 +57,8 @@ struct libipm_priv
     const char *(*msgno_to_str)(unsigned short msgno);
     unsigned short out_msgno;
     unsigned short out_param_count;
+    unsigned short out_fd_count;
+    int out_fds[MAX_FD_PER_MSG];
     unsigned short in_msgno;
     unsigned short in_param_count;
 };

libipm/libipm_send.c

@@ -306,6 +306,47 @@ append_char_ptr_type(char c, struct trans *trans, va_list *argptr)
     return rv;
 }
 
+/**************************************************************************//**
+ * Add a file descriptor to the output stream
+ *
+ * @param c Type letter which triggered the call
+ * @param trans libipm transport
+ * @param argptr Pointer to value in argument stack (promoted to int)
+ * @return != 0 for error
+ */
+static enum libipm_status
+append_fd_type(char c, va_list *argptr, struct trans *trans)
+{
+    enum libipm_status rv = E_LI_SUCCESS;
+    struct stream *s = trans->out_s;
+    struct libipm_priv *priv = (struct libipm_priv *)trans->extra_data;
+    int fd = va_arg(*argptr, int);
+    if (fd < 0)
+    {
+        log_append_error(trans, "File descriptor cannot be < 0");
+        rv = E_LI_PROGRAM_ERROR;
+    }
+    else if (!s_check_rem_out(s, 1))
+    {
+        log_append_error(trans,
+                         "Not enough space in output buffer for '%c'", c);
+        rv = E_LI_BUFFER_OVERFLOW;
+    }
+    else if (priv->out_fd_count >= MAX_FD_PER_MSG)
+    {
+        log_append_error(trans,
+                         "Too many file descriptors for '%c'", c);
+        rv = E_LI_TOO_MANY_FDS;
+    }
+    else
+    {
+        out_uint8(s, c);
+        priv->out_fds[priv->out_fd_count++] = fd;
+    }
+
+    return rv;
+}
+
 /**************************************************************************//**
  * Append a fixed size block to the output stream
  *
@@ -405,6 +446,10 @@ libipm_msg_out_appendv(struct trans *trans, const char *format, va_list *argptr)
                     rv = append_char_ptr_type(c, trans, argptr);
                     break;
 
+                case 'h':
+                    rv = append_fd_type(c, argptr, trans);
+                    break;
+
                 case 'B':
                     rv = append_fsb_type(c, trans, argptr);
                     break;
@@ -441,6 +486,7 @@ init_output_buffer(struct trans *trans, unsigned short msgno)
 
     priv->out_msgno = msgno;
     priv->out_param_count = 0;
+    priv->out_fd_count = 0;
 }
 
 /*****************************************************************************/