kernel-netlink: Use PAGE_SIZE as default size for the netlink receive buffer

The kernel uses NLMSG_GOODSIZE as default buffer size, which defaults to
the PAGE_SIZE if it is lower than 8192 or to that value otherwise.

In some cases (e.g. for dump messages) the kernel might use up to 16k
for messages, which might require increasing this value.

diff --git a/conf/plugins/kernel-netlink.opt b/conf/plugins/kernel-netlink.opt
index 4338a5fbde732a3d0e33f59ab2662bd5bb3ecc2a..6adefd8defd52cb3d823d4f2a705021caef5870f 100644 (file)
--- a/conf/plugins/kernel-netlink.opt
+++ b/conf/plugins/kernel-netlink.opt
@@ -1,4 +1,4 @@
-charon.plugins.kernel-netlink.buflen = 4096
+charon.plugins.kernel-netlink.buflen = <min(PAGE_SIZE, 8192)>
        Buffer size for received Netlink messages.
 
 charon.plugins.kernel-netlink.fwmark =

diff --git a/src/libhydra/plugins/kernel_netlink/kernel_netlink_shared.c b/src/libhydra/plugins/kernel_netlink/kernel_netlink_shared.c
index 238de82b30fe0c8e204f0754b192a3826fd54b72..f7ce992a36d940f13f1b940aa7b9597f6fbee9ca 100644 (file)
--- a/src/libhydra/plugins/kernel_netlink/kernel_netlink_shared.c
+++ b/src/libhydra/plugins/kernel_netlink/kernel_netlink_shared.c
@@ -571,7 +571,7 @@ netlink_socket_t *netlink_socket_create(int protocol, enum_name_t *names,
                .protocol = protocol,
                .names = names,
                .buflen = lib->settings->get_int(lib->settings,
-                                                       "%s.plugins.kernel-netlink.buflen", 4096, lib->ns),
+                                                       "%s.plugins.kernel-netlink.buflen", 0, lib->ns),
                .timeout = lib->settings->get_int(lib->settings,
                                                        "%s.plugins.kernel-netlink.timeout", 0, lib->ns),
                .retries = lib->settings->get_int(lib->settings,
@@ -582,6 +582,16 @@ netlink_socket_t *netlink_socket_create(int protocol, enum_name_t *names,
                .parallel = parallel,
        );
 
+       if (!this->buflen)
+       {
+               long pagesize = sysconf(_SC_PAGESIZE);
+               if (pagesize == -1)
+               {
+                       pagesize = 4096;
+               }
+               /* base this on NLMSG_GOODSIZE */
+               this->buflen = min(pagesize, 8192);
+       }
        if (this->socket == -1)
        {
                DBG1(DBG_KNL, "unable to create netlink socket");