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@@ -815,16 +815,12 @@ The exit status is:
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As DHCP uses low port numbers (67 for DHCPv4 relays and
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547 for DHCPv6), running perfdhcp with non-root privileges will
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usually result in the error message similar to this:
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-
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<screen><userinput>$./perfdhcp -4 -l eth3 -r 100 all</userinput>
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Error running perfdhcp: Failed to bind socket 3 to 172.16.1.2/port=67
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</screen>
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-
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The '-L' command line switch allows the use of a custom local port.
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However, although the following command line will work:
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-
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<screen><userinput>$./perfdhcp -4 -l eth3 -r 100 -L 10067 all</userinput></screen>
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-
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in the standard configuration no responses will be received
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from the DHCP server because the server responds to default relay
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port 67. A way to overcome this issue is to run
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@@ -1007,7 +1003,7 @@ std deviation: 5.876 ms
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collected packets: 0
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</screen>
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There are now no packet drops, confirming that the server is able to
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- handle a load of 100 leases/second.
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+ handle a load of 100 leases/second.
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Note that the last parameter (-R 30) configures perfdhcp to simulate
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traffic from 30 distinct clients.
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</para>
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@@ -1017,8 +1013,17 @@ collected packets: 0
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<para>
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By default the DHCP messages are formed with default options. With
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template files, it is possible to define a custom packet format.
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- </para>
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- <para>
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+ </para>
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+ <para>
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+ The template file names are specified with <![CDATA[-T<template-file>]]>
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+ command line option. This option can be specified zero, one or two times.
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+ The first occurence of this option refers to DISCOVER or SOLICIT message
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+ and the second occurence refers to REQUEST (DHCPv4 or DHCPv6) message.
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+ If -T option occurs only once the DISCOVER or SOLICIT message will be
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+ created from the template and the REQUEST message will be created
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+ dynamically (without the template). Note that each template file
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+ holds data for exactly one DHCP message type. Templates for multiple
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+ message types must not be combined in the single file.
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The content in template files is encoded in hexadecimal format.
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perfdhcp forms the packet by replacing parts of the binary stream read
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from the file with variable data such as elapsed time, hardware address, DUID
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@@ -1068,6 +1073,19 @@ collected packets: 0
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template</para></listitem>
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</itemizedlist>
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</para>
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+ <para>
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+ The offsets of options indicate where they begin in the packet.
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+ The only exception from this rule is <![CDATA[-O<random-offset>]]>
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+ option that specifies the end of the DUID (DHCPv6) or MAC address
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+ (DHCPv4). Depending on the number of simulated clients
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+ (see <![CDATA[-R<random-range>]]> command line option) perfdhcp
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+ will be randomizing bytes in packet buffer starting from this
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+ position backwards. For the number of simulated clients
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+ <![CDATA[<=]]> 256 only one octet (at random-offset position)
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+ will be ranomized, for the number of clients <![CDATA[<=]]> 65536
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+ two octets (at random-offset and random-offset-1)
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+ will be randmized etc.
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+ </para>
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</section>
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</section>
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</chapter>
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Marcin Siodelski