core/icmp/LiteEthICMPEcho: Verify packet length before storing in buffer and drop if too long for configurated depth.

liteeth/common.py

@@ -88,11 +88,11 @@ ipv4_header = Header(ipv4_header_fields, ipv4_header_length, swap_field_bytes=Tr
 
 # ICMP Constants/Header ----------------------------------------------------------------------------
 
-icmp_protocol      = 0x01
-icmp_type_ping_reply = 0
+icmp_protocol          = 0x01
+icmp_type_ping_reply   = 0
 icmp_type_ping_request = 8
-icmp_header_length = 8
-icmp_header_fields = {
+icmp_header_length     = 8
+icmp_header_fields     = {
     "msgtype":  HeaderField(0, 0,  8),
     "code":     HeaderField(1, 0,  8),
     "checksum": HeaderField(2, 0, 16),

liteeth/core/icmp.py

@@ -105,7 +105,8 @@ class LiteEthICMPRX(LiteXModule):
                 "quench",
                 "data",
                 "error",
-                "last_be"}),
+                "last_be"
+            }),
             source.ip_address.eq(sink.ip_address),
             source.length.eq(sink.length - icmp_header.length),
         ]
@@ -141,7 +142,13 @@ class LiteEthICMPEcho(LiteXModule):
             buffered      = True
         )
         self.comb += [
-            sink.connect(self.buffer.sink),
+            # Connect to buffer when length <= buffer's depth.
+            If(sink.length <= fifo_depth,
+                sink.connect(self.buffer.sink)
+            # Else drop.
+            ).Else(
+                sink.ready.eq(1)
+            ),
             self.buffer.source.connect(source, omit={"checksum"}),
             self.source.msgtype.eq(icmp_type_ping_reply),
             self.source.checksum.eq(self.buffer.source.checksum + 0x800 + (self.buffer.source.checksum >= 0xf800))

liteeth/core/ip.py

@@ -235,7 +235,7 @@ class LiteEthIPRX(LiteXModule):
                 "data",
                 "error",
                 "last_be"}),
-            source.length.eq(depacketizer.source.total_length - (0x5*4)),
+            source.length.eq(depacketizer.source.total_length - ipv4_header_length),
             source.ip_address.eq(depacketizer.source.sender_ip),
         ]
         fsm.act("RECEIVE",