NET_ALIAS device aliasing v0.5x
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NET_ALIAS device aliasing v0.5x
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===============================
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===============================
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The main step taken in versions 0.40+ is the implementation of a
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The main step taken in versions 0.40+ is the implementation of a
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device aliasing mechanism that creates *actual* devices.
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device aliasing mechanism that creates *actual* devices.
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This development includes NET_ALIAS (generic aliasing) plus IP_ALIAS
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This development includes NET_ALIAS (generic aliasing) plus IP_ALIAS
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(specific IP) support.
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(specific IP) support.
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From version 0.50, dynamic configuration of max alias per device and
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From version 0.50, dynamic configuration of max alias per device and
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tx/rx stats for aliases added.
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tx/rx stats for aliases added.
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Also fixed inter-alias routing and arping problems.
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Also fixed inter-alias routing and arping problems.
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Features
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Features
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--------
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--------
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o ACTUAL alias devices created & inserted in dev chain
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o ACTUAL alias devices created & inserted in dev chain
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o AF_ independent: net_alias_type objects. Generic aliasing engine.
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o AF_ independent: net_alias_type objects. Generic aliasing engine.
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o AF_INET optimized
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o AF_INET optimized
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o hashed alias address lookup
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o hashed alias address lookup
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o net_alias_type objs registration/unreg., module-ables.
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o net_alias_type objs registration/unreg., module-ables.
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o /proc/net/aliases & /proc/net/alias_types entries
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o /proc/net/aliases & /proc/net/alias_types entries
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o /proc/sys/net/core/net_alias_max entry (affects hash table size
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o /proc/sys/net/core/net_alias_max entry (affects hash table size
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also)
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also)
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o tx/rx stats
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o tx/rx stats
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o IP alias implementation: static or runtime module.
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o IP alias implementation: static or runtime module.
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Usage (IP aliasing)
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Usage (IP aliasing)
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-------------------
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-------------------
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A very first step to test if you are running a net_alias-ed kernel
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A very first step to test if you are running a net_alias-ed kernel
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is to check /proc/net/aliases & /proc/net/alias_types entries:
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is to check /proc/net/aliases & /proc/net/alias_types entries:
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# cat /proc/net/alias*
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# cat /proc/net/alias*
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For IP aliasing you must have IP_ALIAS support included by
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For IP aliasing you must have IP_ALIAS support included by
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static linking ('y' to CONFIG_IP_ALIAS? question), or runtime module
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static linking ('y' to CONFIG_IP_ALIAS? question), or runtime module
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insertion ('m'):
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insertion ('m'):
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# insmod /usr/src/linux/modules/ip_alias.o (2.0.xx) or
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# insmod /usr/src/linux/modules/ip_alias.o (2.0.xx) or
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# modprobe ip_alias.o
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# modprobe ip_alias.o
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Also, dynamic loading is supported (kerneld).
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Also, dynamic loading is supported (kerneld).
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You should have the following line in /etc/conf.modules (not needed
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You should have the following line in /etc/conf.modules (not needed
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for newer modutils):
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for newer modutils):
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alias net_alias-2 ip_alias
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alias net_alias-2 ip_alias
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Module options
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Module options
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--------------
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--------------
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From 0.5x ip_alias module supports a new option ("no_sel" symbol).
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From 0.5x ip_alias module supports a new option ("no_sel" symbol).
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If no_sel is set (default is 0), alias association (device selection) with
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If no_sel is set (default is 0), alias association (device selection) with
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foreign addresses will be disabled.
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foreign addresses will be disabled.
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You will get:
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You will get:
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- Faster operation by avoiding completely routing lookups.
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- Faster operation by avoiding completely routing lookups.
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Due to the "logical nature" of aliasing, netdevice SELection can only be
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Due to the "logical nature" of aliasing, netdevice SELection can only be
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done based on info from network layer. When packet dst address isn't
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done based on info from network layer. When packet dst address isn't
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one of my addresses, I query the routing table to see which netdevice
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one of my addresses, I query the routing table to see which netdevice
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would be selected for packet _source_ address. This option avoids
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would be selected for packet _source_ address. This option avoids
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doing so, and you must consider using it if you *only* have same-net
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doing so, and you must consider using it if you *only* have same-net
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aliases (common usage).
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aliases (common usage).
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You will loose:
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You will loose:
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- Inter-alias routing
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- Inter-alias routing
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- Proxyarp over aliases
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- Proxyarp over aliases
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To activate:
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To activate:
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# insmod ip_alias.o no_sel=1
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# insmod ip_alias.o no_sel=1
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or
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or
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# modprobe ip_alias.o no_sel=1
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# modprobe ip_alias.o no_sel=1
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or
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or
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add the following line to /etc/conf.modules:
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add the following line to /etc/conf.modules:
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options ip_alias no_sel=1
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options ip_alias no_sel=1
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o Alias creation.
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o Alias creation.
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Alias creation is done by 'magic' iface naming: eg. to create a
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Alias creation is done by 'magic' iface naming: eg. to create a
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200.1.1.1 alias for eth0 ...
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200.1.1.1 alias for eth0 ...
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# ifconfig eth0:0 200.1.1.1 etc,etc....
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# ifconfig eth0:0 200.1.1.1 etc,etc....
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~~ -> request alias #0 creation (if it not exists) for eth0
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~~ -> request alias #0 creation (if it not exists) for eth0
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and routing stuff also ...
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and routing stuff also ...
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# route add -host 200.1.1.1 dev eth0:0 (if same IP network as
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# route add -host 200.1.1.1 dev eth0:0 (if same IP network as
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main device)
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main device)
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# route add -net 200.1.1.0 dev eth0:0 (if completely new network wanted
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# route add -net 200.1.1.0 dev eth0:0 (if completely new network wanted
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for eth0:0)
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for eth0:0)
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o Alias deletion.
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o Alias deletion.
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Also done by magic naming, eg:
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Also done by magic naming, eg:
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# ifconfig eth0:0- 0 (maybe any address)
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# ifconfig eth0:0- 0 (maybe any address)
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~~~ -> will delete alias (note '-' after dev name)
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~~~ -> will delete alias (note '-' after dev name)
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alias device is closed before deletion, so all network stuff that
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alias device is closed before deletion, so all network stuff that
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points to it (routes, arp entries, ...) will be released.
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points to it (routes, arp entries, ...) will be released.
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o Alias (re-)configuring
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o Alias (re-)configuring
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Aliases *are* devices, so you configure and refer to them as usual (ifconfig,
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Aliases *are* devices, so you configure and refer to them as usual (ifconfig,
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route, etc).
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route, etc).
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o PROCfs entries
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o PROCfs entries
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2 entries are added to help fetching alias runtime configuration:
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2 entries are added to help fetching alias runtime configuration:
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a) /proc/net/alias_types
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a) /proc/net/alias_types
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Will show you alias_types registered (ie. address families that
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Will show you alias_types registered (ie. address families that
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can be aliased).
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can be aliased).
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eg. for IP aliasing with 1 alias configured:
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eg. for IP aliasing with 1 alias configured:
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# cat /proc/net/alias_types
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# cat /proc/net/alias_types
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type name n_attach
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type name n_attach
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2 ip 1
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2 ip 1
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b) /proc/net/aliases
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b) /proc/net/aliases
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Will show aliased devices info, eg (same as above):
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Will show aliased devices info, eg (same as above):
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# cat /proc/net/aliases
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# cat /proc/net/aliases
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device family address
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device family address
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eth0:0 2 200.1.1.1
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eth0:0 2 200.1.1.1
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o PROCfs dynamic configuration (from v0.50)
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o PROCfs dynamic configuration (from v0.50)
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You can now change the max aliases per device limit via
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You can now change the max aliases per device limit via
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/proc/sys/net/core/net_alias_max entry (default=256)
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/proc/sys/net/core/net_alias_max entry (default=256)
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# cat /proc/sys/net/core/net_alias_max
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# cat /proc/sys/net/core/net_alias_max
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256
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256
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# echo 1000 > /proc/sys/net/core/net_alias_max
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# echo 1000 > /proc/sys/net/core/net_alias_max
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# cat /proc/sys/net/core/net_alias_max
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# cat /proc/sys/net/core/net_alias_max
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1000
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1000
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# _
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# _
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With this funcionality you can disable net_alias creation from now on
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With this funcionality you can disable net_alias creation from now on
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# echo 0 > /proc/sys/net/core/net_alias_max
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# echo 0 > /proc/sys/net/core/net_alias_max
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The new aliasing limit is considered (grabbed) when creating the
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The new aliasing limit is considered (grabbed) when creating the
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FIRST alias for the main device.
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FIRST alias for the main device.
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Eg:
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Eg:
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# echo 10 > /proc/sys/net/core/net_alias_max
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# echo 10 > /proc/sys/net/core/net_alias_max
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# ifconfig eth0:0 xx.xx.xx.xx (first alias creation for eth0,
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# ifconfig eth0:0 xx.xx.xx.xx (first alias creation for eth0,
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eth0 will 'remember' max==10)
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eth0 will 'remember' max==10)
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# echo 1000 > /proc/sys/net/core/net_alias_max
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# echo 1000 > /proc/sys/net/core/net_alias_max
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# ifconfig eth0:999 xx.xx.xx.xx
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# ifconfig eth0:999 xx.xx.xx.xx
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SIOCIFSADDR: No such device
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SIOCIFSADDR: No such device
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Of course these semantics can be changed, please let me know.
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Of course these semantics can be changed, please let me know.
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Configuration changes get logged as usual (klogd -> /var/log/messages)
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Configuration changes get logged as usual (klogd -> /var/log/messages)
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o Alias devices rx/tx stats
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o Alias devices rx/tx stats
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Fake rx/tx stats are accounted:
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Fake rx/tx stats are accounted:
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- TX
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- TX
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When the packet is ``switched'' from logical alias device to
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When the packet is ``switched'' from logical alias device to
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physical device, tx counter gets incremented.
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physical device, tx counter gets incremented.
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- RX
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- RX
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When an incoming packet's address equals alias network device's addr it
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When an incoming packet's address equals alias network device's addr it
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gets ``switched'' from physical to logical device, rx counter gets
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gets ``switched'' from physical to logical device, rx counter gets
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incr.
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incr.
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Please NOTE that for ``same'' network alias devices you usually have
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Please NOTE that for ``same'' network alias devices you usually have
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one net-route through physical device (eg. eth0), so output pkts
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one net-route through physical device (eg. eth0), so output pkts
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will NOT pass down via alias device (so, no tx++ will occur).
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will NOT pass down via alias device (so, no tx++ will occur).
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Also NOTE that currently ifconfig does not handle the ``:'' of alias devices
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Also NOTE that currently ifconfig does not handle the ``:'' of alias devices
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names, a little patch solves the problem:
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names, a little patch solves the problem:
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--- ifconfig.c.dist Tue Apr 4 17:58:32 1995
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--- ifconfig.c.dist Tue Apr 4 17:58:32 1995
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+++ ifconfig.c Fri Oct 25 13:11:23 1996
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+++ ifconfig.c Fri Oct 25 13:11:23 1996
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@@ -243,7 +243,12 @@
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@@ -243,7 +243,12 @@
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bp++;
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bp++;
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if(strncmp(bp,ifname,strlen(ifname))==0 && bp[strlen(ifname)]==':')
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if(strncmp(bp,ifname,strlen(ifname))==0 && bp[strlen(ifname)]==':')
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{
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{
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- bp=strchr(bp,':');
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- bp=strchr(bp,':');
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+ /*
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+ /*
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+ * start bp at ifname end to prevent ':' ambiguity
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+ * start bp at ifname end to prevent ':' ambiguity
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+ * with alias devices (eg. eth0:0)
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+ * with alias devices (eg. eth0:0)
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+ *
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+ *
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+ */
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+ */
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+ bp+=strlen(ifname);
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+ bp+=strlen(ifname);
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bp++;
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bp++;
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sscanf(bp,"%d %d %d %d %d %d %d %d %d %d %d",
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sscanf(bp,"%d %d %d %d %d %d %d %d %d %d %d",
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&ife->stats.rx_packets,
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&ife->stats.rx_packets,
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Relationship with main device
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Relationship with main device
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-----------------------------
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-----------------------------
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- On main device closing, all aliases will be closed and freed.
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- On main device closing, all aliases will be closed and freed.
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- Each new alias created is inserted in dev_chain just before next
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- Each new alias created is inserted in dev_chain just before next
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main device (aliases get 'stacked' after main_dev), eg:
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main device (aliases get 'stacked' after main_dev), eg:
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lo->eth0->eth0:0->eth0:2->eth1->0
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lo->eth0->eth0:0->eth0:2->eth1->0
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If eth0 is unregistered, all it aliases will also be:
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If eth0 is unregistered, all it aliases will also be:
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lo->eth1->0
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lo->eth1->0
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Contact
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Contact
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-------
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-------
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Please e-mail me:
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Please e-mail me:
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Juan Jose Ciarlante or
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Juan Jose Ciarlante or
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Acknowledments
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Acknowledments
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--------------
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--------------
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Special thanks to Claudia for all her love an patience.
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Special thanks to Claudia for all her love an patience.
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Also thanks to Antonio Trevi~o great human being
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Also thanks to Antonio Trevi~o great human being
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and un*x guru.
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and un*x guru.
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; local variables:
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; local variables:
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; mode: indented-text
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; mode: indented-text
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; mode: auto-fill
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; mode: auto-fill
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; end:
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; end:
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