ifplugd: use a larger netlink buffer

function                                             old     new   delta
check_existence_through_netlink                      310     321     +11

Signed-off-by: Tito Ragusa <farmatito@tiscali.it>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 10 insertions, 4 deletions

diff --git a/networking/ifplugd.c b/networking/ifplugd.c
index 3cdc2c9d2..b578f4c61 100644
--- a/networking/ifplugd.c
+++ b/networking/ifplugd.c
@@ -451,20 +451,24 @@ static smallint detect_link(void)
 static NOINLINE int check_existence_through_netlink(void)
 {
         int iface_len;
-        char replybuf[1024];
+        /* Buffer was 1K, but on linux-3.9.9 it was reported to be too small.
+         * netlink.h: "limit to 8K to avoid MSG_TRUNC when PAGE_SIZE is very large".
+         * Note: on error returns (-1) we exit, no need to free replybuf.
+         */
+        enum { BUF_SIZE = 8 * 1024 };
+        char *replybuf = xmalloc(BUF_SIZE);
 
         iface_len = strlen(G.iface);
         while (1) {
                 struct nlmsghdr *mhdr;
                 ssize_t bytes;
 
-                bytes = recv(netlink_fd, &replybuf, sizeof(replybuf), MSG_DONTWAIT);
+                bytes = recv(netlink_fd, replybuf, BUF_SIZE, MSG_DONTWAIT);
                 if (bytes < 0) {
                         if (errno == EAGAIN)
-                                return G.iface_exists;
+                                goto ret;
                         if (errno == EINTR)
                                 continue;
-
                         bb_perror_msg("netlink: recv");
                         return -1;
                 }
@@ -507,6 +511,8 @@ static NOINLINE int check_existence_through_netlink(void)
                 }
         }
 
+ ret:
+        free(replybuf);
         return G.iface_exists;
 }