Contents of /trunk/mkinitrd-magellan/busybox/docs/ifupdown_design.txt
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Sun May 30 11:32:42 2010 UTC (14 years, 4 months ago) by niro
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Sun May 30 11:32:42 2010 UTC (14 years, 4 months ago) by niro
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File size: 1649 byte(s)
-updated to busybox-1.16.1 and enabled blkid/uuid support in default config
1 | This document is meant to convince you to not use ifup/ifdown. |
2 | |
3 | |
4 | The general problem with ifupdown is that it is "copulated in vertical |
5 | fashion" by design. It tries to do the job of shell script in C, |
6 | and this is invariably doomed to fail. You need ifup/ifdown |
7 | to be adaptable by local admins, and C is an extremely poor choice |
8 | for that. |
9 | |
10 | We are doomed to have problems with ifup/ifdown. Just look as this code: |
11 | |
12 | static const struct dhcp_client_t ext_dhcp_clients[] = { |
13 | { "dhcpcd", "<up cmd>", "<down cmd>" }, |
14 | { "dhclient", ........ }, |
15 | { "pump", ........ }, |
16 | { "udhcpc", ........ }, |
17 | }; |
18 | |
19 | static int dhcp_down(struct interface_defn_t *ifd, execfn *exec) |
20 | { |
21 | #if ENABLE_FEATURE_IFUPDOWN_EXTERNAL_DHCP |
22 | int i ; |
23 | for (i = 0; i < ARRAY_SIZE(ext_dhcp_clients); i++) { |
24 | if (exists_execable(ext_dhcp_clients[i].name)) |
25 | return execute(ext_dhcp_clients[i].stopcmd, ifd, exec); |
26 | } |
27 | bb_error_msg("no dhcp clients found, using static interface shutdown"); |
28 | return static_down(ifd, exec); |
29 | #elif ENABLE_UDHCPC |
30 | return execute("kill " |
31 | "`cat /var/run/udhcpc.%iface%.pid` 2>/dev/null", ifd, exec); |
32 | #else |
33 | return 0; /* no dhcp support */ |
34 | #endif |
35 | } |
36 | |
37 | How the hell it is supposed to work reliably this way? Just imagine that |
38 | admin is using pump and ifup/ifdown. It works. Then, for whatever reason, |
39 | admin installs dhclient, but does NOT use it. ifdown will STOP WORKING, |
40 | just because it will see installed dhclient binary in e.g. /usr/bin/dhclient! |
41 | This is stupid. |
42 | |
43 | I seriously urge people to not use ifup/ifdown. |
44 | Use something less brain damaged. |