UDP memory accounting and limitation (take 6)

Hello,

This is the latest patch set of UDP memory accounting and limitation.

The number of pages for socket buffer is limited up to /proc/sys/net/ipv4/udp_mem. I removed the minimal limit number to use the feature from the former patch set (take5). And udp_init() is introduced to calculate default value.

In addition, I added /proc/sys/net/ipv4/udp_rmem and /proc/sys/net/ipv4/udp_wmem to be able to allocate minimum buffer to each socket.

As a result, UDP packet is drooped when the number of pages for socket buffer is beyond the limit and the socket already consumes minimum buffer.

Detailed change log is below.

Changelog take 5 -> take 6:

* removed minimal limit of /proc/sys/net/udp_mem
* added udp_init() for default value calculation of parameters
* added /proc/sys/net/udp_rmem and /proc/sys/net/udp_rmem
* added limitation code to ip_ufo_append_data()
* improved accounting for receiving packet
* fixed typos
* rebased to 2.6.24-rc1

Changelog take 4 -> take 5:

* removing unnessesary EXPORT_SYMBOLs
* adding minimal limit of /proc/sys/net/udp_mem
* bugfix of UDP limit affecting protocol other than UDP
* introducing __ip_check_max_skb_pages()
* using CTL_UNNUMBERED
* adding udp_mem usage to Documentation/networking/ip_sysctl.txt

Best regards,
Hideo Aoki

--
Hitachi Computer Products (America) Inc.