add log for possible ip fragmentation

src/udprelay.c

@@ -639,10 +639,9 @@ static void remote_recv_cb(EV_P_ ev_io *w, int revents)
         goto CLEAN_UP;
     }
 
-    // Drop large packets > default MTU
-    if (buf_len > MTU) {
-        LOGE("[udp] drop large packets, size: %d", (int)buf_len);
-        goto CLEAN_UP;
+    // packet size > default MTU
+    if (verbose && buf_len > MTU) {
+        LOGE("[udp] possible ip fragment, size: %d", (int)buf_len);
     }
 
 #ifdef UDPRELAY_LOCAL
@@ -833,10 +832,9 @@ static void server_recv_cb(EV_P_ ev_io *w, int revents)
 #endif
 #endif
 
-    // Drop large packets > default MTU
-    if (buf_len > MTU) {
-        LOGE("[udp] drop large packets, size: %d", (int)buf_len);
-        goto CLEAN_UP;
+    // packet size > default MTU
+    if (verbose && buf_len > MTU) {
+        LOGE("[udp] possible ip fragment, size: %d", (int)buf_len);
     }
 
     /*

src/udprelay.h

@@ -37,9 +37,9 @@
 
 #include "common.h"
 
-#define MAX_UDP_PACKET_SIZE (2 * 1024) // large enough for a typical MTU 1500
+#define MAX_UDP_PACKET_SIZE (65507)
 
-#define MTU 1421 // 1492 - 1 - 28 - 2 - 40 = 1421, the default MTU for UDP relay
+#define MTU 1397 // 1492 - 1 - 28 - 2 - 64 = 1397, the default MTU for UDP relay
 
 struct server_ctx {
     ev_io io;