1 | This document is meant to convince you to not use ifup/ifdown.
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2 |
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3 |
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4 | The general problem with ifupdown is that it is "copulated in vertical
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5 | fashion" by design. It tries to do the job of shell script in C,
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6 | and this is invariably doomed to fail. You need ifup/ifdown
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7 | to be adaptable by local admins, and C is an extremely poor choice
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8 | for that.
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9 |
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10 | We are doomed to have problems with ifup/ifdown. Just look as this code:
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11 |
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12 | static const struct dhcp_client_t ext_dhcp_clients[] = {
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13 | { "dhcpcd", "<up cmd>", "<down cmd>" },
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14 | { "dhclient", ........ },
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15 | { "pump", ........ },
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16 | { "udhcpc", ........ },
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17 | };
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18 |
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19 | static int dhcp_down(struct interface_defn_t *ifd, execfn *exec)
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20 | {
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21 | #if ENABLE_FEATURE_IFUPDOWN_EXTERNAL_DHCP
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22 | int i ;
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23 | for (i = 0; i < ARRAY_SIZE(ext_dhcp_clients); i++) {
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24 | if (exists_execable(ext_dhcp_clients[i].name))
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25 | return execute(ext_dhcp_clients[i].stopcmd, ifd, exec);
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26 | }
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27 | bb_error_msg("no dhcp clients found, using static interface shutdown");
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28 | return static_down(ifd, exec);
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29 | #elif ENABLE_UDHCPC
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30 | return execute("kill "
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31 | "`cat /var/run/udhcpc.%iface%.pid` 2>/dev/null", ifd, exec);
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32 | #else
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33 | return 0; /* no dhcp support */
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34 | #endif
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35 | }
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36 |
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37 | How the hell it is supposed to work reliably this way? Just imagine that
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38 | admin is using pump and ifup/ifdown. It works. Then, for whatever reason,
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39 | admin installs dhclient, but does NOT use it. ifdown will STOP WORKING,
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40 | just because it will see installed dhclient binary in e.g. /usr/bin/dhclient!
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41 | This is stupid.
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42 |
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43 | I seriously urge people to not use ifup/ifdown.
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44 | Use something less brain damaged.
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