Hi,
I am writing a plugin that handles two new PCAP-NG block types - details here:
https://wiki.wireshark.org/Adding%20Support%20for%20a%20New%20Block%20Type
I'm using Guy's code that adds support for plugins to handle pcap-ng block
types, described in https://code.wireshark.org/review/#/c/1775/
I have written a read block handler and registered it with Wireshark using
register_pcapng_block_type_handler() and the handler gets called correctly.
Once the block has been read by my handler, I want Wireshark to continue to
process it, but currently the block is ignored and Wireshark just moves on to
the next block.
The blocks are read via a while loop in the pcapng_read(...) function of
pcapng.c. After calling a function to read the block there is a "switch
(wblock.type)" section of code that decides what next to do with the block. My
new block is not defined as a switch case (not surprising), but I believe the
default case should take into account the fact that a block type may have been
registered. The code in this area currently looks like this:
switch (wblock.type) {
case(BLOCK_TYPE_SHB):
pcapng_debug("pcapng_read: another section header block");
g_array_append_val(wth->shb_hdrs, wblock.block);
break;
case(BLOCK_TYPE_PB):
case(BLOCK_TYPE_SPB):
case(BLOCK_TYPE_EPB):
case(BLOCK_TYPE_SYSDIG_EVENT):
case(BLOCK_TYPE_SYSDIG_EVF):
/* packet block - we've found a packet */
goto got_packet;
case(BLOCK_TYPE_IDB):
/* A new interface */
pcapng_debug("pcapng_read: block type BLOCK_TYPE_IDB");
pcapng_process_idb(wth, pcapng, &wblock);
wtap_block_free(wblock.block);
break;
case(BLOCK_TYPE_NRB):
/* More name resolution entries */
pcapng_debug("pcapng_read: block type BLOCK_TYPE_NRB");
if (wth->nrb_hdrs == NULL) {
wth->nrb_hdrs = g_array_new(FALSE, FALSE,
sizeof(wtap_block_t));
}
g_array_append_val(wth->nrb_hdrs, wblock.block);
break;
case(BLOCK_TYPE_ISB):
/* Another interface statistics report */
pcapng_debug("pcapng_read: block type BLOCK_TYPE_ISB");
if_stats_mand_block =
(wtapng_if_stats_mandatory_t*)wtap_block_get_mandatory_data(wblock.block);
... lines deleted ...
}
wtap_block_free(wblock.block);
break;
default:
/* XXX - improve handling of "unknown" blocks */
pcapng_debug("pcapng_read: Unknown block type 0x%08x",
wblock.type);
break;
}
}
got_packet:
/*pcapng_debug("Read length: %u Packet length: %u", bytes_read,
wth->phdr.caplen);*/
pcapng_debug("pcapng_read: data_offset is finally %" G_GINT64_MODIFIER "d",
*data_offset);
return TRUE;
I believe that the default condition should check for a plugin registered block
type and then goto got_packet. Also, as the code stands we never free
wblock.block.
Is this a bug, or is my understanding of what's intended wrong?
Thanks and regards...Paul
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