From b7b353acdc492109e455a69448cdef3cb72ee176 Mon Sep 17 00:00:00 2001
From: "Nicholas J. Kain" <nicholas@kain.us>
Date: Wed, 12 Mar 2014 15:07:37 -0400
Subject: [PATCH] Store the interface index in the client_config before forking
 off the subprocesses.  ndhc-ifch can then use the stored interface index when
 setting the interface ip/subnet/broadcast via netlink instead of having to
 use ioctl to re-fetch the interface index.

---
 ndhc/ifset.c | 34 ++--------------------------------
 ndhc/ndhc.c  | 19 ++++++++++---------
 2 files changed, 12 insertions(+), 41 deletions(-)

diff --git a/ndhc/ifset.c b/ndhc/ifset.c
index 075952f..0c35924 100644
--- a/ndhc/ifset.c
+++ b/ndhc/ifset.c
@@ -112,29 +112,6 @@ static int add_rtattr(struct nlmsghdr *n, size_t max_length, int type,
     return 0;
 }
 
-static int get_ifindex(const char *name)
-{
-    struct ifreq ifr;
-    int sk, err;
-
-    if (!name)
-        return -1;
-
-    sk = socket(PF_INET, SOCK_DGRAM, 0);
-    if (sk < 0)
-        return -1;
-
-    memset(&ifr, 0, sizeof ifr);
-    strnkcpy(ifr.ifr_name, name, sizeof ifr.ifr_name);
-
-    err = ioctl(sk, SIOCGIFINDEX, &ifr);
-    close(sk);
-    if (err < 0)
-        return -1;
-
-    return ifr.ifr_ifindex;
-}
-
 // 32-bit position values are relatively prime to 37, so the residue mod37
 // gives a unique mapping for each value.  Gives correct result for v=0.
 static int trailz(uint32_t v)
@@ -163,7 +140,7 @@ void perform_ip_subnet_bcast(const char *str_ipaddr,
     struct sockaddr_nl nl_addr;
     struct nlmsghdr *header;
     struct ifaddrmsg *ifaddrmsg;
-    int nls, ifidx, r;
+    int nls, r;
     uint8_t prefixlen;
 
     if (!str_ipaddr) {
@@ -177,13 +154,6 @@ void perform_ip_subnet_bcast(const char *str_ipaddr,
         return;
     }
 
-    ifidx = get_ifindex(client_config.interface);
-    if (ifidx < 0) {
-        log_line("%s: (%s) can't get interface index",
-                 client_config.interface, __func__);
-        return;
-    }
-
     if (inet_pton(AF_INET, str_ipaddr, &ipaddr) <= 0) {
         log_line("%s: (%s) bad interface ip address: '%s'",
                  client_config.interface, __func__, str_ipaddr);
@@ -220,7 +190,7 @@ void perform_ip_subnet_bcast(const char *str_ipaddr,
     ifaddrmsg->ifa_prefixlen = prefixlen;
     ifaddrmsg->ifa_flags = IFA_F_PERMANENT;
     ifaddrmsg->ifa_scope = RT_SCOPE_UNIVERSE;
-    ifaddrmsg->ifa_index = ifidx;
+    ifaddrmsg->ifa_index = client_config.ifindex;
 
     if (add_rtattr(header, sizeof request, IFA_LOCAL,
                    &ipaddr, sizeof ipaddr) < 0) {
diff --git a/ndhc/ndhc.c b/ndhc/ndhc.c
index 6da240a..ac5c38d 100644
--- a/ndhc/ndhc.c
+++ b/ndhc/ndhc.c
@@ -301,15 +301,6 @@ static void ndhc_main(void) {
         write_pid(pidfile);
     }
 
-    if ((cs.nlFd = nl_open(NETLINK_ROUTE, RTMGRP_LINK, &cs.nlPortId)) < 0) {
-        log_line("FATAL - failed to open netlink socket");
-        exit(EXIT_FAILURE);
-    }
-    if (nl_getifdata(&cs) < 0) {
-        log_line("FATAL - failed to get interface MAC and index");
-        exit(EXIT_FAILURE);
-    }
-
     open_leasefile();
 
     imprison(chroot_dir);
@@ -523,11 +514,21 @@ int main(int argc, char **argv)
     if (!strncmp(chroot_dir, "", sizeof chroot_dir))
         suicide("FATAL - No chroot path specified.  Refusing to run.");
 
+    if ((cs.nlFd = nl_open(NETLINK_ROUTE, RTMGRP_LINK, &cs.nlPortId)) < 0) {
+        log_line("FATAL - failed to open netlink socket");
+        exit(EXIT_FAILURE);
+    }
+    if (nl_getifdata(&cs) < 0) {
+        log_line("FATAL - failed to get interface MAC and index");
+        exit(EXIT_FAILURE);
+    }
+
     create_ipc_pipes();
     pid_t ifch_pid = fork();
     if (ifch_pid == 0) {
         close(pToNdhcR);
         close(pToIfchW);
+        close(cs.nlFd);
         ifch_main();
     } else if (ifch_pid > 0) {
         close(pToIfchR);