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  • Committer: Phil Dennis-Jordan
  • Date: 2017-07-21 08:03:43 UTC
  • mfrom: (1.1.1)
  • Revision ID: phil@philjordan.eu-20170721080343-2yr2vdj7713czahv
New upstream release 2.9.0.

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roms/u-boot/doc/README.link-local
 
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 Link-local IP address auto-configuration
 
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Negotiate with other link-local clients on the local network
 
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for an address that doesn't require explicit configuration.
 
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This is especially useful if a DHCP server cannot be guaranteed
 
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to exist in all environments that the device must operate.
 
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This is an implementation of RFC3927.
 
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----------
 
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 Commands
 
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----------
 
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When CONFIG_CMD_LINK_LOCAL is defined in the board config file,
 
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the "linklocal" command is available.  This running this will
 
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take approximately 5 seconds while the address is negotiated.
 
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------------------------
 
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 Environment interation
 
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------------------------
 
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The "llipaddr" variable is set with the most recently
 
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negotiated address and is preferred in future negotiations.
 
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The "ipaddr", "netmask", and "gatewayip" variables are set
 
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after successful negotiation to enable network access.
 
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-------------
 
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 Limitations
 
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-------------
 
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RFC3927 requires that addresses are continuously checked to
 
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avoid conflicts, however this can only happen when the NetLoop
 
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is getting called.  It is possible for a conflict to go undetected
 
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until a command that accesses the network is executed.
 
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Using NetConsole is one way to ensure that NetLoop is always
 
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processing packets and monitoring for conflicts.
 
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This is also not a concern if the feature is use to connect
 
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directly to another machine that may not be running a DHCP server.
 
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----------------
 
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 Example script
 
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----------------
 
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This script allows use of DHCP and/or Link-local controlled
 
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by env variables.  It depends on CONFIG_CMD_LINK_LOCAL, CONFIG_CMD_DHCP,
 
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and CONFIG_BOOTP_MAY_FAIL.
 
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If both fail or are disabled, static settings are used.
 
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#define CONFIG_EXTRA_ENV_SETTINGS \
 
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        "ipconfigcmd=if test \\\"$dhcpenabled\\\" -ne 0;"               \
 
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                "then "                                                 \
 
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                        "dhcpfail=0;dhcp || dhcpfail=1;"                \
 
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                "else "                                                 \
 
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                        "dhcpfail=-1;"                                  \
 
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                "fi;"                                                   \
 
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                "if test \\\"$linklocalenabled\\\" -ne 0 -a "           \
 
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                        "\\\"$dhcpfail\\\" -ne 0;"                      \
 
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                "then "                                                 \
 
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                        "linklocal;"                                    \
 
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                        "llfail=0;"                                     \
 
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                "else "                                                 \
 
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                        "llfail=-1;"                                    \
 
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                "fi;"                                                   \
 
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                "if test \\\"$llfail\\\" -ne 0 -a "                     \
 
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                        "\\\"$dhcpfail\\\" -ne 0; "                     \
 
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                "then "                                                 \
 
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                        "setenv ipaddr $sipaddr; "                      \
 
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                        "setenv netmask $snetmask; "                    \
 
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                        "setenv gatewayip $sgatewayip; "                \
 
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                "fi;\0"                                                 \