isisd: tighten checks on ISIS pdu length

  * isisd/isis_pdu.c: Fix problem where isisd would crash if it
    received a LAN IIH with the 'pdu length' field set to zero.
    Similar problems can occur in parsing other ISIS PDUs as well --
    check that the PDU length in an ISIS hello, LSP or SNP packet is
    at least as big as the size of the respective fixed header.
1 file changed