[pxe] Discard queued PXE UDP packets when under memory pressure
The PXE UDP receive queue may grow without limit if the PXE NBP does
not call PXENV_UDP_READ sufficiently frequently.
Fix by implementing a cache discarder for received PXE UDP packets
(similar to the TCP cache discarder).
Reported-by: Tal Shorer <shorer@amazon.com>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
diff --git a/src/arch/x86/interface/pxe/pxe_udp.c b/src/arch/x86/interface/pxe/pxe_udp.c
index 5a04f08..a5d5eb7 100644
--- a/src/arch/x86/interface/pxe/pxe_udp.c
+++ b/src/arch/x86/interface/pxe/pxe_udp.c
@@ -12,6 +12,7 @@
#include <ipxe/uaccess.h>
#include <ipxe/process.h>
#include <ipxe/netdevice.h>
+#include <ipxe/malloc.h>
#include <realmode.h>
#include <pxe.h>
@@ -482,3 +483,28 @@
PXE_API_CALL ( PXENV_UDP_READ, pxenv_udp_read,
struct s_PXENV_UDP_READ ),
};
+
+/**
+ * Discard some cached PXE UDP data
+ *
+ * @ret discarded Number of cached items discarded
+ */
+static unsigned int pxe_udp_discard ( void ) {
+ struct io_buffer *iobuf;
+ unsigned int discarded = 0;
+
+ /* Try to discard the oldest received UDP packet */
+ iobuf = list_first_entry ( &pxe_udp.list, struct io_buffer, list );
+ if ( iobuf ) {
+ list_del ( &iobuf->list );
+ free_iob ( iobuf );
+ discarded++;
+ }
+
+ return discarded;
+}
+
+/** PXE UDP cache discarder */
+struct cache_discarder pxe_udp_discarder __cache_discarder ( CACHE_NORMAL ) = {
+ .discard = pxe_udp_discard,
+};
