just set SO_RCVBUF to a small value

and don't bother reading from the socket.

diff --git a/src/lib/util/udp_queue.c b/src/lib/util/udp_queue.c
index 419398f4d8ddc5bfe9b61aa7fded1406d5589481..b531332c7f6daee48e4bc3055d606fadef822152 100644 (file)
--- a/src/lib/util/udp_queue.c
+++ b/src/lib/util/udp_queue.c
@@ -27,6 +27,7 @@
 RCSID("$Id$")
 
 #include <freeradius-devel/util/debug.h>
+#include <freeradius-devel/util/syserror.h>
 
 #include <freeradius-devel/util/socket.h>
 #include <freeradius-devel/util/udp_queue.h>
@@ -124,9 +125,6 @@ fr_udp_queue_t *fr_udp_queue_alloc(TALLOC_CTX *ctx, fr_udp_queue_config_t const
        if (config->interface &&
            (fr_socket_bind(fd, &config->ipaddr, &port, config->interface) < 0)) goto error;
 
-       /*
-        *      Set sendbuf
-        */
 #ifdef SO_SNDBUF
        /*
         *      Set SO_SNDBUF size, if configured to do so.
@@ -143,6 +141,20 @@ fr_udp_queue_t *fr_udp_queue_alloc(TALLOC_CTX *ctx, fr_udp_queue_config_t const
        }
 #endif
 
+#ifdef SO_RCVBUF
+       /*
+        *      Set SO_RECVBUFF to 4K, so that the kernel will quickly
+        *      drop incoming packets.  We don't expect replies, and
+        *      we never check the socket for readability, so this is
+        *      fine.
+        */
+       {
+               int opt = 4096;
+
+               (void) setsockopt(fd, SOL_SOCKET, SO_RCVBUF, &opt, sizeof(int));
+       }
+#endif
+
        uq = talloc_zero(ctx, fr_udp_queue_t);
        if (!uq) {
        error:
@@ -174,14 +186,6 @@ static void udp_queue_writable(UNUSED fr_event_list_t *el, UNUSED int fd,
 {
        fr_udp_queue_t  *uq = talloc_get_type_abort(uctx, fr_udp_queue_t);
        fr_time_t       now = fr_time();
-       uint8_t         buffer[1];
-
-       /*
-        *      Read and discard any inputs.
-        */
-       while (read(uq->fd, buffer, sizeof(buffer)) > 0) {
-               /* do nothing */
-       }
 
        fr_dlist_foreach_safe(&uq->queue, fr_udp_queue_entry_t, entry) {
                ssize_t rcode;
@@ -266,14 +270,6 @@ int fr_udp_queue_write(TALLOC_CTX *ctx, fr_udp_queue_t *uq, uint8_t const *packe
        if (!uq->blocked) {
                int retries = 0;
                ssize_t rcode;
-               char buffer[1];
-
-               /*
-                *      Read and discard any inputs.
-                */
-               while (read(uq->fd, buffer, sizeof(buffer)) > 0) {
-                       /* do nothing */
-               }
 
 retry:
                rcode = sendto(uq->fd, packet, packet_len, 0, (struct sockaddr *) &sockaddr, socklen);