Method decodeLabel

Server/src/bgp/MPReachAttr.cpp:411–455

* Decode label from NLRI data * * \details * Decodes the labels from the NLRI data into labels string * * \param [in] data Pointer to the start of the label + prefixes to be parsed * \param [in] len Length of the data in bytes to be read * \param [out] labels Reference to string that will be updated with labels delimited by comm

 *
 */
inline uint16_t MPReachAttr::decodeLabel(u_char *data, uint16_t len, std::string &labels) {
    int read_size = 0;
    typedef union {
        struct {
            uint8_t   ttl     : 8;          // TTL - not present since only 3 octets are used
            uint8_t   bos     : 1;          // Bottom of stack
            uint8_t   exp     : 3;          // EXP - not really used
            uint32_t  value   : 20;         // Label value
        } decode;
        uint32_t  data;                 // Raw label - 3 octets only per RFC3107
    } mpls_label;

    mpls_label label;

    labels.clear();

    u_char *data_ptr = data;

    // the label is 3 octets long
    while (read_size <= len)
    {
        bzero(&label, sizeof(label));

        memcpy(&label.data, data_ptr, 3);
        bgp::SWAP_BYTES(&label.data);     // change to host order

        data_ptr += 3;
        read_size += 3;

        ostringstream convert;
        convert << label.decode.value;
        labels.append(convert.str());

        //printf("label data = %x\n", label.data);
        if (label.decode.bos == 1 or label.data == 0x80000000 /* withdrawn label as 32bits instead of 24 */
                or label.data == 0 /* l3vpn seems to use zero instead of rfc3107 suggested value */) {
            break;               // Reached EoS

        } else {
            labels.append(",");
        }
    }

    return read_size;
}

} /* namespace bgp_msg */