Remove some duplicate DTLS code.

In a couple of functions, a sequence number would be calculated twice.

Additionally, in |dtls1_process_out_of_seq_message|, we know that
|frag_len| <= |msg_hdr->msg_len| so the later tests for |frag_len <
msg_hdr->msg_len| can be more clearly written as |frag_len !=
msg_hdr->msg_len|, since that's the only remaining case.
Reviewed-by: NMatt Caswell <matt@openssl.org>
Reviewed-by: NEmilia Käsper <emilia@openssl.org>

ssl/d1_both.c

@@ -604,7 +604,7 @@ static unsigned long dtls1_max_handshake_message_len(const SSL *s)
 	}
 
 static int
-dtls1_reassemble_fragment(SSL *s, struct hm_header_st* msg_hdr, int *ok)
+dtls1_reassemble_fragment(SSL *s, const struct hm_header_st* msg_hdr, int *ok)
 	{
 	hm_fragment *frag = NULL;
 	pitem *item = NULL;
@@ -687,10 +687,6 @@ dtls1_reassemble_fragment(SSL *s, struct hm_header_st* msg_hdr, int *ok)
 
 	if (item == NULL)
 		{
-		memset(seq64be,0,sizeof(seq64be));
-		seq64be[6] = (unsigned char)(msg_hdr->seq>>8);
-		seq64be[7] = (unsigned char)(msg_hdr->seq);
-
 		item = pitem_new(seq64be, frag);
 		if (item == NULL)
 			{
@@ -716,7 +712,7 @@ err:
 
 
 static int
-dtls1_process_out_of_seq_message(SSL *s, struct hm_header_st* msg_hdr, int *ok)
+dtls1_process_out_of_seq_message(SSL *s, const struct hm_header_st* msg_hdr, int *ok)
 {
 	int i=-1;
 	hm_fragment *frag = NULL;
@@ -736,7 +732,7 @@ dtls1_process_out_of_seq_message(SSL *s, struct hm_header_st* msg_hdr, int *ok)
 	/* If we already have an entry and this one is a fragment,
 	 * don't discard it and rather try to reassemble it.
 	 */
-	if (item != NULL && frag_len < msg_hdr->msg_len)
+	if (item != NULL && frag_len != msg_hdr->msg_len)
 		item = NULL;
 
 	/* Discard the message if sequence number was already there, is
@@ -761,7 +757,7 @@ dtls1_process_out_of_seq_message(SSL *s, struct hm_header_st* msg_hdr, int *ok)
 		}
 	else
 		{
-		if (frag_len < msg_hdr->msg_len)
+		if (frag_len != msg_hdr->msg_len)
 			return dtls1_reassemble_fragment(s, msg_hdr, ok);
 
 		if (frag_len > dtls1_max_handshake_message_len(s))
@@ -784,10 +780,6 @@ dtls1_process_out_of_seq_message(SSL *s, struct hm_header_st* msg_hdr, int *ok)
 				goto err;
 			}
 
-		memset(seq64be,0,sizeof(seq64be));
-		seq64be[6] = (unsigned char)(msg_hdr->seq>>8);
-		seq64be[7] = (unsigned char)(msg_hdr->seq);
-
 		item = pitem_new(seq64be, frag);
 		if ( item == NULL)
 			goto err;