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| -rw-r--r-- | docs/ifupdown_design.txt | 44 |
1 files changed, 44 insertions, 0 deletions
diff --git a/docs/ifupdown_design.txt b/docs/ifupdown_design.txt new file mode 100644 index 000000000..9df579289 --- /dev/null +++ b/docs/ifupdown_design.txt @@ -0,0 +1,44 @@ +This document is meant to convince you to not use ifup/ifdown. + + +The general problem with ifupdown is that it is "copulated in vertical +fashion" by design. It tries to do the job of shell script in C, +and this is invariably doomed to fail. You need ifup/ifdown +to be adaptable by local admins, and C is an extremely poor choice +for that. + +We are doomed to have problems with ifup/ifdown. Just look as this code: + +static const struct dhcp_client_t ext_dhcp_clients[] = { + { "dhcpcd", "<up cmd>", "<down cmd>" }, + { "dhclient", ........ }, + { "pump", ........ }, + { "udhcpc", ........ }, +}; + +static int dhcp_down(struct interface_defn_t *ifd, execfn *exec) +{ +#if ENABLE_FEATURE_IFUPDOWN_EXTERNAL_DHCP + int i ; + for (i = 0; i < ARRAY_SIZE(ext_dhcp_clients); i++) { + if (exists_execable(ext_dhcp_clients[i].name)) + return execute(ext_dhcp_clients[i].stopcmd, ifd, exec); + } + bb_error_msg("no dhcp clients found, using static interface shutdown"); + return static_down(ifd, exec); +#elif ENABLE_APP_UDHCPC + return execute("kill " + "`cat /var/run/udhcpc.%iface%.pid` 2>/dev/null", ifd, exec); +#else + return 0; /* no dhcp support */ +#endif +} + +How the hell it is supposed to work reliably this way? Just imagine that +admin is using pump and ifup/ifdown. It works. Then, for whatever reason, +admin installs dhclient, but does NOT use it. ifdown will STOP WORKING, +just because it will see installed dhclient binary in e.g. /usr/bin/dhclient! +This is stupid. + +I seriously urge people to not use ifup/ifdown. +Use something less brain damaged. |