Talk about _recv_fd

1 files changed, 19 insertions, 2 deletions

diff --git a/content/posts/WIP-how-bsd-authentication-works/index.org b/content/posts/WIP-how-bsd-authentication-works/index.org
index 9b17953..5bc90b7 100644
--- a/content/posts/WIP-how-bsd-authentication-works/index.org
+++ b/content/posts/WIP-how-bsd-authentication-works/index.org
@@ -635,10 +635,27 @@
    #+end_src
 
    =_auth_spool='s job is to read data from =fd= and place it in
-   =as->spool=, and to update =as->index= to the length of the data on
-   the spool.
+   =as->spool=, and to update =as->index= with the length of the data
+   on the spool. While spooling it converts newlines to =NUL='s in
+   order to parse the output more easily. It also handles any file
+   descriptors passed through the back channel by sending them to
+   =_recv_fd=.
+
+   #+begin_src c
+   // [...]
+   if (strcasecmp(s, BI_FDPASS) == 0)
+       _recv_fd(as, fd);
+   #+end_src
+
 ** _recv_fd
+   #+begin_src c
+   static void _recv_fd(auth_session_t *as, int fd)
+   #+end_src
 
+   =_recv_fd= reads control messages, also called ancillary data, from
+   =fd= and tried to receive a file descriptor. If it receives one and
+   =as->fd= is equal to =-1=, it sets it to the received file
+   descriptor. Otherwise it closes the received file descriptor.
 * auth_close
   =auth_close= is the function responsible for cleaning up the session
   and taking care of the values returned though the back channel.