Fixes <https://issues.guix.gnu.org/47867>.

This fix was merged upstream
in <https://gitlab.com/gnutls/gnutls/-/merge_requests/1417> and will
be in GnuTLS 3.7.3.  Upstream commit:

commit 110e2172dbef1fbdf7399dab1e80780847b61c0c
Author: Ludovic Courtès <ludo@gnu.org>
Date:   Sat Apr 24 22:02:14 2021 +0200

    guile: Writes to record ports handle EAGAIN/EINTR transparently.

diff --git a/guile/src/core.c b/guile/src/core.c
index a13670fc7b..0926dc8a97 100644
--- a/guile/src/core.c
+++ b/guile/src/core.c
@@ -985,7 +985,10 @@ write_to_session_record_port (SCM port, const void *data, size_t size)
       c_result = gnutls_record_send (c_session, (char *) data + c_sent,
                                      size - c_sent);
       if (EXPECT_FALSE (c_result < 0))
-        scm_gnutls_error (c_result, FUNC_NAME);
+	{
+	  if (c_result != GNUTLS_E_AGAIN && c_result != GNUTLS_E_INTERRUPTED)
+	    scm_gnutls_error (c_result, FUNC_NAME);
+	}
       else
         c_sent += c_result;
     }
@@ -1069,7 +1072,8 @@ read_from_session_record_port (SCM port, SCM dst, size_t start, size_t count)
 #undef FUNC_NAME
 
 /* Return the file descriptor that backs PORT.  This function is called upon a
-   blocking read--i.e., 'read_from_session_record_port' returned -1.  */
+   blocking read--i.e., 'read_from_session_record_port' or
+   'write_to_session_record_port' returned -1.  */
 static int
 session_record_port_fd (SCM port)
 {
@@ -1097,7 +1101,16 @@ write_to_session_record_port (SCM port, SCM src, size_t start, size_t count)
   c_session = scm_to_gnutls_session (session, 1, FUNC_NAME);
   data = (char *) SCM_BYTEVECTOR_CONTENTS (src) + start;
 
-  result = gnutls_record_send (c_session, data, count);
+  do
+    result = gnutls_record_send (c_session, data, count);
+  while (result == GNUTLS_E_INTERRUPTED
+	 || (result == GNUTLS_E_AGAIN
+	     && !SCM_GNUTLS_SESSION_TRANSPORT_IS_FD (c_session)));
+
+  if (result == GNUTLS_E_AGAIN
+      && SCM_GNUTLS_SESSION_TRANSPORT_IS_FD (c_session))
+    /* Tell Guile that reading would block.  */
+    return (size_t) -1;
 
   if (EXPECT_FALSE (result < 0))
     scm_gnutls_error (result, FUNC_NAME);
f='/guix/log/doc?id=53ef4bf53775cf80959000667c5bdb7f4d7b6232'>doc</a>/<a href='/guix/log/doc/he-config-bare-bones.scm?id=53ef4bf53775cf80959000667c5bdb7f4d7b6232'>he-config-bare-bones.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/doc/he-config-bare-bones.scm?id=53ef4bf53775cf80959000667c5bdb7f4d7b6232&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2022-06-10 22:42:49 +0200'>2022-06-10</span></td><td><a href='/guix/commit/doc/he-config-bare-bones.scm?id=d859d8873ceb3c591210968cfd4c88e26fc89edc'>doc: Update example of a minimalistic home environment.</a><span class='msg-avail'>...<span class='msg-tooltip'>* doc/he-config-bare-bones.scm: Adujst example according to changes in
bash-service-type and home-files-service-type.

Signed-off-by: Ludovic Courtès &lt;ludo@gnu.org&gt;
</span></span></td><td>Andrew Tropin</td></tr>
<tr><td><span title='2021-10-09 19:24:18 +0300'>2021-10-09</span></td><td><a href='/guix/commit/doc/he-config-bare-bones.scm?id=0e8d2df0f1a4ab25c482e1c427c54e19903e62f3'>Move (gnu home-services) to (gnu home services).</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/home-services.scm (%guix-home-root-directory): Replace
gnu/home-services.scm with "gnu/home/services.scm".
Rename to gnu/home/services.scm.
* gnu/local.mk
(GNU_SYSTEM_MODULES): Rename gnu/home-services.scm to gnu/home/services.scm.
* doc/he-config-bare-bones.scm:
Replace (gnu home-services) with (gnu home services).
* gnu/home.scm: Same.
* gnu/home/services/fontutils.scm: Same.
* gnu/home/services/mcron.scm: Same.
* gnu/home/services/shells.scm: Same.
* gnu/home/services/shepherd.scm: Same.
* gnu/home/services/symlink-manager.scm: Same.
* gnu/home/services/xdg.scm: Same.
* guix/scripts/home.scm: Same.
* guix/self.scm: Same.
</span></span></td><td>Oleg Pykhalov</td></tr>
<tr><td><span title='2021-10-08 15:36:18 +0300'>2021-10-08</span></td><td><a href='/guix/commit/doc/he-config-bare-bones.scm?id=ba8ddb348045f81f061a1c7f51c0f7c2b0024e71'>gnu: Move (gnu home-services) to (gnu home services).</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/home-services/configuration.scm: Move the content ...
* gnu/home/services/configuration.scm: ... here.
* doc/guix.texi:
Replace (gnu home-services mcron) with (gnu home services mcron).
Replace (gnu home-services) with (gnu home services).
* gnu/home.scm:
Replace (gnu home-services fontutils) with (gnu services fontutils).
Replace (gnu home-services shells) with (gnu home services shells).
Replace (gnu home-services symlink-manager) with
(gnu home services symlink-manager).
Replace (gnu home-services xdg) with (gnu home services xdg).
* gnu/home-services/fontutils.scm: Rename to gnu/services/fontutils.scm.
* gnu/home-services/mcron.scm: Move to gnu/home/services/mcron.scm.
Replace (gnu home-services shepherd) with (gnu home services shepherd).
* gnu/home-services.scm (%service-type-path):
Search home services in "gnu/services".
* gnu/home-services/shells.scm: Replace (gnu home-services configuration) with
(gnu home services configuration).
Rename to gnu/home/services/shells.scm.
Replace (gnu home-services utils) with (gnu home services utils).
* gnu/home-services/shepherd.scm: Move to gnu/home/services/shepherd.scm.
* gnu/home-services/symlink-manager.scm:
Rename to gnu/home/services/symlink-manager.scm.
* gnu/home-services/utils.scm: Rename to gnu/home/services/utils.scm.
* gnu/home-services/xdg.scm: Rename to gnu/home/services/xdg.scm.
* guix/scripts/home/import.scm:
Replace (gnu home-services bash) with (gnu home services bash).
* gnu/home-services.scm: Update documentation string.
* doc/he-config-bare-bones.scm:
Apply new (gnu home-services ...) modules location.
* gnu/local.mk (GNU_SYSTEM_MODULES): Same.
</span></span></td><td>Oleg Pykhalov</td></tr>
<tr><td><span title='2021-09-09 20:26:51 +0300'>2021-09-09</span></td><td><a href='/guix/commit/doc/he-config-bare-bones.scm?id=aaffa43c1752e062934580f55616e0380963a1be'>doc: Add Guix Home documentation.</a><span class='msg-avail'>...<span class='msg-tooltip'>* doc/guix.texi: Add Guix Home documentation.
* doc/he-config-bare-bones.scm: New file.

Signed-off-by: Oleg Pykhalov &lt;go.wigust@gmail.com&gt;
</span></span></td><td>Andrew Tropin</td></tr>