Ani Sinha <a...@aristanetworks.com> writes: > On Sat, Nov 17, 2012 at 3:33 PM, Eric W. Biederman > <ebied...@xmission.com> wrote: >> the vlan header in packets as we receive them. >> >> The code is correct except for the case of packets in vlan 0. Currently >> the packet reconstruction is ambiguous. The most recent kernels have >> a TP_STATUS_VLAN_VALID flag that can be checked to see if the packet was >> in vlan 0 or if there was no vlan at all. libpcap probably should be >> taught how to handle TP_STATUS_VLAN_VALID so that it can get the vlan 0 >> handling correct. >> > > May be this?
Two things. - TP_STATUS_VLAN_VALID lives in the tp_status field not the tp_vlan_tci field. - To work on older kernels with binaries compiled with newer headers you first want to test for tp_vlan_tci == 0 and then look at the status field for TP_STATUS_VALID. Which means the tests need to look something like: - if (aux->tp_vlan_tci == 0) +#if defined(TP_STATUS_VLAN_VALID) + if ((aux->tp_vlan_tci == 0) && !(aux->tp_status & TP_STATUS_VLAN_VALID)) +#else + if (aux->tp_vlan_tci == 0) /* this is ambigious but without the + TP_STATUS_VLAN_VALID flag, there is + nothing that we can do */ +#endif #ifdef HAVE_TPACKET2 - if (handle->md.tp_version == TPACKET_V2 && h.h2->tp_vlan_tci && + if (handle->md.tp_version == TPACKET_V2 && +#if defined(TP_STATUS_VLAN_VALID) + (h.h2->tp_vlan_tci || (h.h2->tp_status & TP_STATUS_VALID)) && +#else + h.h2->tp_vlan_tci && +#endif Eric _______________________________________________ tcpdump-workers mailing list tcpdump-workers@lists.tcpdump.org https://lists.sandelman.ca/mailman/listinfo/tcpdump-workers
