diff options
Diffstat (limited to 'Documentation/networking/packet_mmap.txt')
| -rw-r--r-- | Documentation/networking/packet_mmap.txt | 30 |
1 files changed, 28 insertions, 2 deletions
diff --git a/Documentation/networking/packet_mmap.txt b/Documentation/networking/packet_mmap.txt index 8e48e3b14227..723bf3d33a6e 100644 --- a/Documentation/networking/packet_mmap.txt +++ b/Documentation/networking/packet_mmap.txt @@ -517,8 +517,6 @@ where 'tpacket_version' can be TPACKET_V1 (default), TPACKET_V2, TPACKET_V3. TPACKET_V1: - Default if not otherwise specified by setsockopt(2) - RX_RING, TX_RING available - - VLAN metadata information available for packets - (TP_STATUS_VLAN_VALID) TPACKET_V1 --> TPACKET_V2: - Made 64 bit clean due to unsigned long usage in TPACKET_V1 @@ -526,6 +524,13 @@ TPACKET_V1 --> TPACKET_V2: userspace and the like - Timestamp resolution in nanoseconds instead of microseconds - RX_RING, TX_RING available + - VLAN metadata information available for packets + (TP_STATUS_VLAN_VALID, TP_STATUS_VLAN_TPID_VALID), + in the tpacket2_hdr structure: + - TP_STATUS_VLAN_VALID bit being set into the tp_status field indicates + that the tp_vlan_tci field has valid VLAN TCI value + - TP_STATUS_VLAN_TPID_VALID bit being set into the tp_status field + indicates that the tp_vlan_tpid field has valid VLAN TPID value - How to switch to TPACKET_V2: 1. Replace struct tpacket_hdr by struct tpacket2_hdr 2. Query header len and save @@ -953,6 +958,27 @@ int main(int argc, char **argp) } ------------------------------------------------------------------------------- ++ PACKET_QDISC_BYPASS +------------------------------------------------------------------------------- + +If there is a requirement to load the network with many packets in a similar +fashion as pktgen does, you might set the following option after socket +creation: + + int one = 1; + setsockopt(fd, SOL_PACKET, PACKET_QDISC_BYPASS, &one, sizeof(one)); + +This has the side-effect, that packets sent through PF_PACKET will bypass the +kernel's qdisc layer and are forcedly pushed to the driver directly. Meaning, +packet are not buffered, tc disciplines are ignored, increased loss can occur +and such packets are also not visible to other PF_PACKET sockets anymore. So, +you have been warned; generally, this can be useful for stress testing various +components of a system. + +On default, PACKET_QDISC_BYPASS is disabled and needs to be explicitly enabled +on PF_PACKET sockets. + +------------------------------------------------------------------------------- + PACKET_TIMESTAMP ------------------------------------------------------------------------------- |