Xen出现Too many frags以及fatal error; disabling device日志，子系统断网解决办法

Xen有些时候一些GUEST OS系统正常运行中但是网络断了，直接重启后网络又恢复了。
从dmesg里面查看相应的信息发现出现了Too many frags

vif vif-162-0: vifXEN_NAME.0: Too many frags
vif vif-162-0: vifXEN_NAME.0: fatal error; disabling device

google了一下从一些mail list里面找到了解决办法，就是关闭tx和tso以及gso.

先查看网卡

ethtool -k 网卡

运行命令会得到以下返回数据(一些机器返回的结果可能会有出入)

[root@node75 ~]# ethtool -k eth0
Features for eth0:
rx-checksumming: on
tx-checksumming: on
	tx-checksum-ipv4: off [fixed]
	tx-checksum-ip-generic: on
	tx-checksum-ipv6: off [fixed]
	tx-checksum-fcoe-crc: off [fixed]
	tx-checksum-sctp: off [fixed]
scatter-gather: on
	tx-scatter-gather: on
	tx-scatter-gather-fraglist: off [fixed]
tcp-segmentation-offload: on
	tx-tcp-segmentation: on
	tx-tcp-ecn-segmentation: off [fixed]
	tx-tcp6-segmentation: on
udp-fragmentation-offload: off [fixed]
generic-segmentation-offload: on
generic-receive-offload: on
large-receive-offload: off [fixed]
rx-vlan-offload: on
tx-vlan-offload: on
ntuple-filters: off [fixed]
receive-hashing: on
highdma: on [fixed]
rx-vlan-filter: off [fixed]
vlan-challenged: off [fixed]
tx-lockless: off [fixed]
netns-local: off [fixed]
tx-gso-robust: off [fixed]
tx-fcoe-segmentation: off [fixed]
fcoe-mtu: off [fixed]
tx-nocache-copy: on
loopback: off [fixed]
rx-fcs: off
rx-all: off

执行以下命令关闭tx tso gso

ethtool -K eth0 tx off tso off gso off

关闭后再用ethtool查看网卡会看到下面三个都为off关闭
tx-checksumming: off
tcp-segmentation-offload: off
generic-segmentation-offload: off

tso的全称是tcp-segmentation-offload， gso的全称是generic-segmentation-offload
关于更多相关信息可以查阅http://en.wikipedia.org/wiki/Large_segment_offload

以上内容是在基于Centos6 X64，kernel 3的环境撰写。