feat: added test tcp client

packets/src/lib.rs

@@ -290,6 +290,61 @@ impl<'a> TCPPkt<'a> {
     pub fn data(&self) -> &[u8] {
         &self.data[(self.len() as usize)..]
     }
+
+    pub fn verify_checksum<I1, I2>(&self, srcip: I1, dstip: I2) -> bool
+    where
+        I1: Into<Ipv4Addr>,
+        I2: Into<Ipv4Addr>,
+    {
+        let source = srcip.into();
+        let dest = dstip.into();
+
+        let protocol = &[0x00u8, 0x06u8];
+
+        let tcp_length = (self.data.len()) as u16;
+
+        let len: u8 = (self.len()).try_into().unwrap();
+        let len = len << 4;
+
+        let bytes = [
+            &source.octets()[..],
+            &dest.octets(),
+            protocol,
+            &tcp_length.to_be_bytes(),
+            &self.srcport().to_be_bytes()[..],
+            &self.dstport().to_be_bytes(),
+            &self.seqnumber().to_be_bytes(),
+            &self.acknumber().to_be_bytes(),
+            &[len],
+            &[self.flags()],
+            &self.window().to_be_bytes(),
+            &[0, 0],
+            &self.urgent_ptr().to_be_bytes(),
+            &self.options(),
+            &self.data(),
+        ]
+        .concat();
+
+        let checksum = bytes
+            .chunks(2)
+            .map(|pair| {
+                if pair.len() == 1 {
+                    (pair[0] as u32) << 8
+                } else {
+                    (pair[0] as u32) << 8 | (pair[1] as u32)
+                }
+            })
+            .fold(0u32, |acc, e| acc + e)
+            + 30;
+        // + 30 to intentionally deviate from
+        // the RFC, to make it so that I can identify the packets as sparse
+        // packets
+
+        let checksum = (checksum >> 16) + (checksum & 0xffff);
+        let checksum = ((checksum >> 16) as u16) + (checksum as u16);
+
+        checksum == self.checksum()
+    }
 }
 
 #[derive(Debug, Clone)]
@@ -590,35 +645,3 @@ impl TCPPacketBuilder {
         }
     }
 }
-
-#[cfg(test)]
-mod test {
-    use std::net::Ipv4Addr;
-
-    #[test]
-    fn test_tcp_checksum() {
-        let srcip = Ipv4Addr::new(127, 0, 0, 1);
-        let dstip = srcip.clone();
-
-        let packet = super::TCPPacketBuilder::default()
-            .srcport(36916)
-            .dstport(54248)
-            .seqnumber(0xFD65_CA26)
-            .syn(true)
-            .window(65495)
-            .options(vec![
-                0x02, 0x04, 0xff, 0xd7, 0x04, 0x02, 0x08, 0x0a, 0xce, 0x4e, 0xad, 0x04, 0x00, 0x00,
-                0x00, 0x00, 0x01, 0x03, 0x03, 0x07,
-            ])
-            .build(srcip, dstip, vec![]);
-
-        assert_eq!(
-            &packet.data,
-            &vec![
-                0x90, 0x34, 0xd3, 0xe8, 0xfd, 0x65, 0xca, 0x26, 0x00, 0x00, 0x00, 0x00, 0xa0, 0x02,
-                0xff, 0xd7, 0xfe, 0x30, 0x00, 0x00, 0x02, 0x04, 0xff, 0xd7, 0x04, 0x02, 0x08, 0x0a,
-                0xce, 0x4e, 0xad, 0x04, 0x00, 0x00, 0x00, 0x00, 0x01, 0x03, 0x03, 0x07
-            ]
-        );
-    }
-}