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ng_tcpmss.4freebsd
Langue: en
Version: 300624 (debian - 07/07/09)
Section: 4 (Pilotes et protocoles réseau)
BSD mandoc
NAME
ng_tcpmss - netgraph node to adjust TCP MSS optionSYNOPSIS
In netgraph.h In netgraph/ng_tcpmss.hDESCRIPTION
The tcpmss node type is designed to alter the Maximum Segment Size option of TCP packets. This node accepts an arbitrary number of hooks. Initially a new hook is considered unconfigured. The NG_TCPMSS_CONFIG control message is used to configure a hook.CONTROL MESSAGES
This node type supports the generic control messages, plus the following.- NGM_TCPMSS_CONFIG (config )
- This control message configures node to do given MSS adjusting on a particular hook. It requires the Vt struct ng_tcpmss_config to be supplied as an argument:
struct ng_tcpmss_config { char inHook[NG_HOOKSIZ]; char outHook[NG_HOOKSIZ]; uint16_t maxMSS; }
This means: packets received on inHook would be checked for TCP MSS option and the latter would be reduced down to maxMSS if it exceeds maxMSS After that, packets would be sent to hook outHook
- NGM_TCPMSS_GET_STATS (getstats )
- This control message obtains statistics for a given hook. The statistics are returned in Vt struct ng_tcpmss_hookstat :
struct ng_tcpmss_hookstat { uint64_t Octets; /* total bytes */ uint64_t Packets; /* total packets */ uint16_t maxMSS; /* maximum MSS */ uint64_t SYNPkts; /* TCP SYN packets */ uint64_t FixedPkts; /* changed packets */ };
- NGM_TCPMSS_CLR_STATS (clrstats )
- This control message clears statistics for a given hook.
- NGM_TCPMSS_GETCLR_STATS (getclrstats )
- This control message obtains and clears statistics for a given hook.
EXAMPLES
In the following example, packets are injected into the tcpmss node using the ng_ipfw4 node.# Create tcpmss node and connect it to ng_ipfw node ngctl mkpeer ipfw: tcpmss 100 qqq # Adjust MSS to 1452 ngctl msg ipfw:100 config '{ inHook="qqq" outHook="qqq" maxMSS=1452 }' # Divert traffic into tcpmss node ipfw add 300 netgraph 100 tcp from any to any tcpflags syn out via fxp0 # Let packets continue with ipfw after being hacked sysctl net.inet.ip.fw.one_pass=0
SHUTDOWN
This node shuts down upon receipt of an NGM_SHUTDOWN control message, or when all hooks have been disconnected.SEE ALSO
netgraph(4), ng_ipfw4HISTORY
The node type was implemented in Fx 6.0 .AUTHORS
An Alexey Popov Aq lollypop@flexuser.ru An Gleb Smirnoff Aq glebius@FreeBSD.orgBUGS
When running on SMP, system statistics may be broken.Contenus ©2006-2024 Benjamin Poulain
Design ©2006-2024 Maxime Vantorre