source: branches/2.2.9/mindi-busybox/docs/ifupdown_design.txt @ 3320

Last change on this file since 3320 was 3320, checked in by Bruno Cornec, 6 years ago
  • Re-add (thanks git BTW) the 2.2.9 branch which had been destroyed in the move to 3.0
  • Property svn:eol-style set to native
File size: 1.5 KB
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1This document is meant to convince you to not use ifup/ifdown.
2
3
4The general problem with ifupdown is that it is "copulated in vertical
5fashion" by design. It tries to do the job of shell script in C,
6and this is invariably doomed to fail. You need ifup/ifdown
7to be adaptable by local admins, and C is an extremely poor choice
8for that.
9
10We are doomed to have problems with ifup/ifdown. Just look as this code:
11
12static const struct dhcp_client_t ext_dhcp_clients[] = {
13    { "dhcpcd", "<up cmd>", "<down cmd>" },
14    { "dhclient", ........ },
15    { "pump", ........ },
16    { "udhcpc", ........ },
17};
18
19static 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
37How the hell it is supposed to work reliably this way? Just imagine that
38admin is using pump and ifup/ifdown. It works. Then, for whatever reason,
39admin installs dhclient, but does NOT use it. ifdown will STOP WORKING,
40just because it will see installed dhclient binary in e.g. /usr/bin/dhclient!
41This is stupid.
42
43I seriously urge people to not use ifup/ifdown.
44Use something less brain damaged.
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