Remove some redundant code

Reviewed-by: Hugo Landau <hlandau@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from #18132)

ssl/record/rec_layer_d1.c

@@ -184,9 +184,6 @@ static void dtls_unbuffer_record(SSL_CONNECTION *s)
         }
 #endif
 
-        /* Set proper sequence number for mac calculation */
-        memcpy(&(s->rlayer.read_sequence[2]), &(rdata->seq_num[2]), 6);
-
         OPENSSL_free(item->data);
         pitem_free(item);
     }
@@ -854,10 +851,8 @@ int do_dtls1_write(SSL_CONNECTION *sc, int type, const unsigned char *buf,
 void dtls1_reset_seq_numbers(SSL_CONNECTION *s, int rw)
 {
     unsigned char *seq;
-    unsigned int seq_bytes = sizeof(s->rlayer.read_sequence);
 
     if (rw & SSL3_CC_READ) {
-        seq = s->rlayer.read_sequence;
         s->rlayer.d->r_epoch++;
 
         /*
@@ -870,7 +865,6 @@ void dtls1_reset_seq_numbers(SSL_CONNECTION *s, int rw)
         memcpy(s->rlayer.d->last_write_sequence, seq,
                sizeof(s->rlayer.write_sequence));
         s->rlayer.d->w_epoch++;
+        memset(seq, 0, sizeof(s->rlayer.write_sequence));
     }
-
-    memset(seq, 0, seq_bytes);
 }

ssl/record/rec_layer_s3.c

@@ -44,7 +44,6 @@ void RECORD_LAYER_clear(RECORD_LAYER *rl)
 
     ssl3_release_write_buffer(rl->s);
 
-    RECORD_LAYER_reset_read_sequence(rl);
     RECORD_LAYER_reset_write_sequence(rl);
 
     if (rl->rrlmethod != NULL)
@@ -82,11 +81,6 @@ int RECORD_LAYER_write_pending(const RECORD_LAYER *rl)
         && SSL3_BUFFER_get_left(&rl->wbuf[rl->numwpipes - 1]) != 0;
 }
 
-void RECORD_LAYER_reset_read_sequence(RECORD_LAYER *rl)
-{
-    memset(rl->read_sequence, 0, sizeof(rl->read_sequence));
-}
-
 void RECORD_LAYER_reset_write_sequence(RECORD_LAYER *rl)
 {
     memset(rl->write_sequence, 0, sizeof(rl->write_sequence));

ssl/record/record.h

@@ -178,8 +178,7 @@ typedef struct record_layer_st {
     /* number of bytes submitted */
     size_t wpend_ret;
     const unsigned char *wpend_buf;
-    /* TODO(RECLAYER): Why do we need this */
-    unsigned char read_sequence[SEQ_NUM_SIZE];
+
     unsigned char write_sequence[SEQ_NUM_SIZE];
     /* Count of the number of consecutive warning alerts received */
     unsigned int alert_count;
@@ -223,7 +222,6 @@ void RECORD_LAYER_release(RECORD_LAYER *rl);
 int RECORD_LAYER_read_pending(const RECORD_LAYER *rl);
 int RECORD_LAYER_processed_read_pending(const RECORD_LAYER *rl);
 int RECORD_LAYER_write_pending(const RECORD_LAYER *rl);
-void RECORD_LAYER_reset_read_sequence(RECORD_LAYER *rl);
 void RECORD_LAYER_reset_write_sequence(RECORD_LAYER *rl);
 int RECORD_LAYER_is_sslv2_record(RECORD_LAYER *rl);
 __owur size_t ssl3_pending(const SSL *s);

ssl/record/record_local.h

@@ -18,7 +18,6 @@
 
 /* Functions/macros provided by the RECORD_LAYER component */
 
-#define RECORD_LAYER_get_read_sequence(rl)      ((rl)->read_sequence)
 #define RECORD_LAYER_get_write_sequence(rl)     ((rl)->write_sequence)
 #define RECORD_LAYER_inc_empty_record_count(rl) ((rl)->empty_record_count++)
 #define RECORD_LAYER_reset_empty_record_count(rl) \