Kernel Study Notes

0.0.0.1. redhat 7 full support itHow redhat 7 said 123456785.5.1. Bridge Zero Copy TransmitZero copy transmit mode is effective on large packet sizes. It typically reduces the host CPU overhead by up

0.1. tcpudmp对 direction的支持。内核代码有一个关键数据结构：skb的pkt_type字段。在收发路径这个域被赋值为PACKET_OUTGOING或者其他。这个值被传递到往用户空间，libpcap根据它判断报文的方向是否是期望的。 0.1.1. pkt_type的可能取值1234524 #define PACKET_HOST 0

vhost net 的目的是为了避免在host kerne上做一次qemu的调度，提升性能。xmit: 让vm的数据报在 host的内核就把报文发送出去。rcv： 0.0.1. 核心数据结构0.0.1.1. vhost_poll是vhost里最关键的一个数据结构。1234567891027 /* Pol> > file (eventfd or socket) */28 /* Note:

0.0.0.1. L2 mode0.0.0.1.1. xmit packet0.0.0.1.1.1. xmit a normal pkt to other phy machine1234==> ipvlan_start_xmit==> ==> ipvlan_xmit_mode_l2==> ==> ==> skb->dev = ipvlan->phy_

0.0.1. test caseWe found ixgbe rx softirq poll function ixgbe_poll was called even without pkt coming.how to prove it and who call it? 0.0.2. analysisBy browse source ixgbe_poll is called, it should

0.0.1. test caseFor ixgbe nic, we want to assign a tx hardware qeueue to each cpu,and the tx softirq should use the corresponding hardware queue. each packet will select a softqueue in dev_queue_xmit,

0.0.1. data structure123457913 static const struct net_device_ops ixgbe_netdev_ops = {...7916 .ndo_start_xmit = ixgbe_xmit_frame,7917 .ndo_select_queue = ixgbe_selec

0.0.1. test case0.0.1.1. On redhat5, Why tcpdump could not work on bonding work.OS: redhat 5.There are two 82599 interfaces eth0 and eth1.These two interfaces are used as slave of bond0,eth1 is backup

0.1. This question should be divided into two parts. 0.1.1. Part 1: adding a route0.1.1.1. Add a direct(link) route0.1.1.2. Add a route with gateway0.1.2. create a socket0.1.2.1. for example ‘connect’

0.0.1. call trace以handle_level_irq为例说明. 1234===> handle_level_irq==> ==> handle_irq_event==> ==> ==> handle_irq_event_percpu==> ==> ==> ==>action->handler 0.0.1.1. wh