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Add extension support with the PINGPONG extension Add extension support. There are two ways to add extensions: 1. as a shared object which will be loaded with ext=<filename> as a parameter to lwwire. See the lwwire_pingpong.c file for details. 2. By doing basically the same thing as a shared object but linking it into the main binary and calling lwwire_register_extension() appropriately.
author William Astle <lost@l-w.ca>
date Sat, 30 Jul 2016 13:16:39 -0600
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1 /*
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2 PINGPONG extension for lwwire
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3 */
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4
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5 #include <stdio.h>
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6 #include "lwwire.h"
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7
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8 /*
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9
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10 NOTE: the __attribute__((used)) tags are there to prevent the functions
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11 from being optimized out as would often be the case with functions declared
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12 static. This could be avoided by removing the static declarations. However,
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13 by declaring everything static except for the lwwire_register() function,
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14 we avoid polluting the global namespace and possibly having conflicts with
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15 other extensions.
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16 */
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17
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18
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19 // this is called to handle an operation for this extension
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20 // it should return nonzero if the operation code (op) is not
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21 // supported. Otherwise, it should implement the operation codes.
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22 __attribute__((used)) static int pingpong_handler(int op)
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23 {
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24 unsigned char buf[1];
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25
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26 if (op > 1 || op < 0)
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27 return -1;
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28 buf[1] = 0x42;
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29 lwwire_write(buf, 1);
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30 return 0;
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31 }
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32
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33 // this will be called when the extension is enabled
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34 // return nonzero if enabling the extension cannot happen for some reason
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35 __attribute__((used)) static int pingpong_enable(void)
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36 {
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37 return 0;
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38 }
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39
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40 // this will be called when an extension is disabled
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41 // if this extension cannot be disabled after it is enabled, it should return
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42 // nonzero; otherwise, this MUST succeed
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43 __attribute__((used)) static int pingpong_disable(void)
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44 {
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45 return 0;
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46 }
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47
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48 // this call should do anything needed to disable the extension
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49 // and anything special that might be needed on a protocol reset
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50 // it will only be called if the extension is enabled when the
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51 // reset occurs. Even if the extension isn't disablable, this call
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52 // MUST disable it and reset things as if the extension was never
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53 // enabled.
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54 __attribute__((used)) static void pingpong_reset(void)
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55 {
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56 }
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57
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58 int lwwire_register(void)
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59 {
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60 fprintf(stderr, "Registering PINGPONG extension\n");
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61 return lwwire_register_extension(0xdf, pingpong_handler, pingpong_enable, pingpong_disable, pingpong_reset);
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62 }