How to display mss value in decimal as column

edit

There are TCP fields for tcp.options.mss and tcp.options.mss_val.
tcp.options.mss_val is BASE_DEC.

packet-tcp.c:

    proto_tree_add_item_ret_uint(exp_tree, hf_tcp_option_mss_val, tvb, offset + 2, 2, ENC_BIG_ENDIAN, &mss);
    proto_item_append_text(item, ": %u bytes", mss);
    tcp_info_append_uint(pinfo, "MSS", mss);

....

        { &hf_tcp_option_mss_val,
          { "MSS Value", "tcp.options.mss_val", FT_UINT16,
            BASE_DEC, NULL, 0x0, NULL, HFILL}},