ipaccess: Drop e1inp_line reference in ipacess_drop()

the bfd->data handles a reference to the e1np_line (obtained through
e1inp_line_get() during bfd setup), so remember to drop it under this
condition.

Related: OS#4624
Change-Id: I418064df04872befe2e936e21768b6ea01263120
diff --git a/src/input/ipaccess.c b/src/input/ipaccess.c
index 5d17839..08b34a4 100644
--- a/src/input/ipaccess.c
+++ b/src/input/ipaccess.c
@@ -92,6 +92,13 @@
 		osmo_fd_unregister(bfd);
 		close(bfd->fd);
 		bfd->fd = -1;
+		/* This is BSC code, ipaccess_drop() is only called for
+		   accepted() sockets, hence the bfd holds a reference to
+		   e1inp_line in ->data that needs to be released */
+		OSMO_ASSERT(bfd->data == line);
+		bfd->data = NULL;
+		e1inp_line_put2(line, "ipa_bfd");
+
 		ret = -ENOENT;
 	}