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Re: datagram source port?
From: |
Robert Pluim |
Subject: |
Re: datagram source port? |
Date: |
Thu, 19 Dec 2019 11:41:41 +0100 |
>>>>> On Thu, 19 Dec 2019 10:12:10 +0100, Mario Lang <address@hidden> said:
Mario> Hi.
Mario> Is it possible to specify the source port for a datagram process?
Mario> I didn't find anything in the elisp Info section about processes.
Mario> And specifying :local [127 0 0 1 1234] didn't work either.
The docstring for make-network-process says:
:local ADDRESS -- ADDRESS is the local address used for the connection.
This parameter is ignored when opening a client process.
Mario> Right now, the port is choosen randomly. That is not ideal for
Mario> certain UDP applications, which match on the source port at the
Mario> receiving end.
That seems fragile. Anyway, given that we have
set-process-datagram-address, I donʼt see why we couldn't add
set-process-datagram-source-address as well. Eli, something like this?
Or we could add an optional parameter to set-process-datagram-address
to mean 'set source'.
(I realize weʼre close to cutting the emacs-27 branch, and it needs
documentation etc)
diff --git a/src/process.c b/src/process.c
index 0f82682ae5..60ccff698a 100644
--- a/src/process.c
+++ b/src/process.c
@@ -2756,6 +2756,43 @@ DEFUN ("process-datagram-address",
Fprocess_datagram_address, Sprocess_datagram_
datagram_address[channel].len);
}
+DEFUN ("set-process-datagram-source-address",
Fset_process_datagram_source_address, Sset_process_datagram_source_address,
+ 2, 2, 0,
+ doc: /* Set the datagram source address for PROCESS to ADDRESS.
+Return nil upon error setting address, ADDRESS otherwise.
+
+If PROCESS is a non-blocking network process that hasn't been fully
+set up yet, this function will block until socket setup has completed. */)
+ (Lisp_Object process, Lisp_Object address)
+{
+ int channel;
+ int family;
+ ptrdiff_t len;
+
+ CHECK_PROCESS (process);
+
+ if (NETCONN_P (process))
+ wait_for_socket_fds (process, "set-process-datagram-source-address");
+
+ if (!DATAGRAM_CONN_P (process))
+ return Qnil;
+
+ channel = XPROCESS (process)->outfd;
+
+ len = get_lisp_to_sockaddr_size (address, &family);
+ if (len == 0 || datagram_address[channel].len != len)
+ return Qnil;
+
+ struct sockaddr sa;
+ conv_lisp_to_sockaddr (family, address, &sa, len);
+ if (bind (channel, &sa, len) != 0)
+ return Qnil;
+
+ Lisp_Object contact = XPROCESS (process)->childp;
+ XPROCESS (process)->childp = Fplist_put (contact, QClocal, address);
+ return address;
+}
+
DEFUN ("set-process-datagram-address", Fset_process_datagram_address,
Sset_process_datagram_address,
2, 2, 0,
doc: /* Set the datagram address for PROCESS to ADDRESS.
@@ -8487,6 +8524,7 @@ syms_of_process (void)
#ifdef DATAGRAM_SOCKETS
defsubr (&Sprocess_datagram_address);
defsubr (&Sset_process_datagram_address);
+ defsubr (&Sset_process_datagram_source_address);
#endif
defsubr (&Saccept_process_output);
defsubr (&Sprocess_send_region);