Hi Dario, 2016-08-26 10:02 GMT+02:00 Dario Lombardo <[email protected]>:
> Hi, > I'm looking into the code of exported_pdu.c and specifically > into export_pdu_create_tags(). The first tag it creates is the tag with > proto_name. The piece of code that I don't understand is > > /* Start by computing size of protocol name as a tag */ > proto_str_len = (int)strlen(proto_name); > > /* Ensure that tag length is a multiple of 4 bytes */ > proto_tag_len = ((proto_str_len + 3) & 0xfffffffc); > > /* Add Tag + length */ > tag_buf_size += (proto_tag_len + 4); > > [...] > > exp_pdu_data->tlv_buffer = (guint8 *)g_malloc0(tag_buf_size); > > Basically, the buffer to store the proto_name tag must be multiple of 4 > bytes. This means that if I use "data", I have "data", but if I use "data1" > I have "data1\x00\x00\x00". What's the rationale behind this? Why is the > alignment to 4 bytes required? > This is inspired by the pcapng specification. You have a complete description of the TLV format used in epan/exported_pdu.h Pascal.
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