gen_pkcs3: add comment explaining rationale

Wondering why you wrote some code and having to grep the source code to find out,
in the same year that you wrote it, is generally a sign of missing information.

Fixed.

1 files changed, 10 insertions, 0 deletions

diff --git a/src/util/gen_pkcs3.c b/src/util/gen_pkcs3.c
index ae7e7610a..4be2c581e 100644
--- a/src/util/gen_pkcs3.c
+++ b/src/util/gen_pkcs3.c
@@ -7,6 +7,16 @@
  * c99 $(pkg-config --cflags openssl) gen_pkcs3.c $(pkg-config --libs openssl)
  */
 
+/*
+ * Rationale:
+ * The Diffie-Hellman primes which are embedded into Exim as named primes for
+ * the tls_dhparam option are in the std-crypto.c file.  The source for those
+ * comes from various RFCs, where they are given in hexadecimal form.
+ *
+ * This tool provides convenient conversion, to reduce the risk of human
+ * error in transcription.
+ */
+
 #include <ctype.h>
 #include <errno.h>
 #include <stdbool.h>