OpenVPN: Authenticate/Decrypt packet error: packet HMAC authentication failed

/* Verify the HMAC */
      if (ctx->hmac)
        {
          int hmac_len;
          uint8_t local_hmac[MAX_HMAC_KEY_LENGTH]; /* HMAC of ciphertext computed locally */
          int in_hmac_len;

          HMAC_Init_ex (ctx->hmac, NULL, 0, NULL, NULL);

          /* Assume the length of the input HMAC */
          hmac_len = HMAC_size (ctx->hmac);

          /* Authentication fails if insufficient data in packet for HMAC */
          if (buf->len < hmac_len)
            CRYPT_ERROR ("missing authentication info");

          HMAC_Update (ctx->hmac, BPTR (buf) + hmac_len,
                       BLEN (buf) - hmac_len);
          HMAC_Final (ctx->hmac, local_hmac, (unsigned int *)&in_hmac_len);
          ASSERT (hmac_len == in_hmac_len);

          /* Compare locally computed HMAC with packet HMAC */ //<<< значит не совпал локально вычисленный HMAC с тем, что у пакета
          if (memcmp (local_hmac, BPTR (buf), hmac_len))
            CRYPT_ERROR ("packet HMAC authentication failed"); //<<< ВОТ ОНО!!!11

          ASSERT (buf_advance (buf, hmac_len));
        }