From a8a761da146d7319f57ea8efe447713325c6ab6a Mon Sep 17 00:00:00 2001
From: "Nicholas J. Kain" <nicholas@kain.us>
Date: Tue, 3 Apr 2012 22:00:47 -0400
Subject: [PATCH] Shrink stack use of nl_getifdata().

---
 ndhc/ndhc.c    |  2 +-
 ndhc/netlink.c | 17 ++++++++++++-----
 ndhc/netlink.h |  2 +-
 3 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/ndhc/ndhc.c b/ndhc/ndhc.c
index b67a507..fcf5744 100644
--- a/ndhc/ndhc.c
+++ b/ndhc/ndhc.c
@@ -353,7 +353,7 @@ int main(int argc, char **argv)
         log_line("FATAL - failed to open netlink socket");
         exit(EXIT_FAILURE);
     }
-    if (nl_getifdata(client_config.interface, &cs) < 0) {
+    if (nl_getifdata(&cs) < 0) {
         log_line("FATAL - failed to get interface MAC and index");
         exit(EXIT_FAILURE);
     }
diff --git a/ndhc/netlink.c b/ndhc/netlink.c
index 2e4fa1c..985b783 100644
--- a/ndhc/netlink.c
+++ b/ndhc/netlink.c
@@ -124,6 +124,7 @@ static int nl_process_msgs(const struct nlmsghdr *nlh, void *data)
     return 1;
 }
 
+/* Destroys contents of nlbuf */
 void handle_nl_message(struct client_state_t *cs)
 {
     ssize_t ret;
@@ -137,12 +138,11 @@ void handle_nl_message(struct client_state_t *cs)
     } while (ret > 0);
 }
 
-int nl_getifdata(const char *ifname, struct client_state_t *cs)
+static int nl_sendgetlink(struct client_state_t *cs)
 {
-    char buf[8192];
-    struct nlmsghdr *nlh = (struct nlmsghdr *)buf;
+    struct nlmsghdr *nlh = (struct nlmsghdr *)nlbuf;
 
-    memset(buf, 0, sizeof buf);
+    memset(nlbuf, 0, sizeof nlbuf);
     nlh->nlmsg_len = NLMSG_LENGTH(sizeof (struct ifinfomsg));
     nlh->nlmsg_type = RTM_GETLINK;
     nlh->nlmsg_flags = NLM_F_REQUEST | NLM_F_ROOT;
@@ -151,9 +151,16 @@ int nl_getifdata(const char *ifname, struct client_state_t *cs)
     struct sockaddr_nl addr = {
         .nl_family = AF_NETLINK,
     };
-    if (sendto(cs->nlFd, buf, nlh->nlmsg_len, 0, (struct sockaddr *)&addr,
+    if (sendto(cs->nlFd, nlbuf, nlh->nlmsg_len, 0, (struct sockaddr *)&addr,
                sizeof addr) == -1)
         return -1;
+    return 0;
+}
+
+int nl_getifdata(struct client_state_t *cs)
+{
+    if (nl_sendgetlink(cs))
+        return -1;
 
     for (int pr = 0; !pr;) {
         pr = poll(&((struct pollfd){.fd=cs->nlFd,.events=POLLIN}), 1, -1);
diff --git a/ndhc/netlink.h b/ndhc/netlink.h
index c39e5d3..d19c407 100644
--- a/ndhc/netlink.h
+++ b/ndhc/netlink.h
@@ -43,6 +43,6 @@ enum {
 extern int nlportid;
 
 void handle_nl_message(struct client_state_t *cs);
-int nl_getifdata(const char *ifname, struct client_state_t *cs);
+int nl_getifdata(struct client_state_t *cs);
 
 #endif /* NK_NETLINK_H_ */