adds back position field to coding-shred-header (#21600)

https://github.com/solana-labs/solana/pull/17004
removed position field from coding-shred-header because as it stands the
field is redundant and unused.
However, with the upcoming changes to erasure coding schema this field
will no longer be redundant and needs to be populated.

core/src/retransmit_stage.rs

@@ -639,19 +639,19 @@ mod tests {
         assert!(should_skip_retransmit(&shred, &shreds_received));
         assert!(should_skip_retransmit(&shred, &shreds_received));
 
-        let shred = Shred::new_empty_coding(slot, index, 0, 1, 1, version);
+        let shred = Shred::new_empty_coding(slot, index, 0, 1, 1, 0, version);
         // Coding at (1, 5) passes
         assert!(!should_skip_retransmit(&shred, &shreds_received));
         // then blocked
         assert!(should_skip_retransmit(&shred, &shreds_received));
 
-        let shred = Shred::new_empty_coding(slot, index, 2, 1, 1, version);
+        let shred = Shred::new_empty_coding(slot, index, 2, 1, 1, 0, version);
         // 2nd unique coding at (1, 5) passes
         assert!(!should_skip_retransmit(&shred, &shreds_received));
         // same again is blocked
         assert!(should_skip_retransmit(&shred, &shreds_received));
 
-        let shred = Shred::new_empty_coding(slot, index, 3, 1, 1, version);
+        let shred = Shred::new_empty_coding(slot, index, 3, 1, 1, 0, version);
         // Another unique coding at (1, 5) always blocked
         assert!(should_skip_retransmit(&shred, &shreds_received));
         assert!(should_skip_retransmit(&shred, &shreds_received));

core/src/window_service.rs

@@ -878,7 +878,15 @@ mod test {
         ));
 
         // coding shreds don't contain parent slot information, test that slot >= root
-        let (common, coding) = Shredder::new_coding_shred_header(5, 5, 5, 6, 6, 0);
+        let (common, coding) = Shredder::new_coding_shred_header(
+            5, // slot
+            5, // index
+            5, // fec_set_index
+            6, // num_data_shreds
+            6, // num_coding_shreds
+            3, // position
+            0, // version
+        );
         let mut coding_shred =
             Shred::new_empty_from_header(common, DataShredHeader::default(), coding);
         Shredder::sign_shred(&leader_keypair, &mut coding_shred);
@@ -954,7 +962,15 @@ mod test {
             std::net::{IpAddr, Ipv4Addr},
         };
         solana_logger::setup();
-        let (common, coding) = Shredder::new_coding_shred_header(5, 5, 5, 6, 6, 0);
+        let (common, coding) = Shredder::new_coding_shred_header(
+            5, // slot
+            5, // index
+            5, // fec_set_index
+            6, // num_data_shreds
+            6, // num_coding_shreds
+            4, // position
+            0, // version
+        );
         let shred = Shred::new_empty_from_header(common, DataShredHeader::default(), coding);
         let mut shreds = vec![shred.clone(), shred.clone(), shred];
         let _from_addr = SocketAddr::new(IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)), 8080);

ledger/src/blockstore.rs

@@ -5554,7 +5554,14 @@ pub mod tests {
         let blockstore = Blockstore::open(ledger_path.path()).unwrap();
 
         let slot = 1;
-        let (shred, coding) = Shredder::new_coding_shred_header(slot, 11, 11, 11, 11, 0);
+        let (shred, coding) = Shredder::new_coding_shred_header(
+            slot, 11, // index
+            11, // fec_set_index
+            11, // num_data_shreds
+            11, // num_coding_shreds
+            8,  // position
+            0,  // version
+        );
         let coding_shred = Shred::new_empty_from_header(shred, DataShredHeader::default(), coding);
 
         let mut erasure_metas = HashMap::new();
@@ -5604,7 +5611,14 @@ pub mod tests {
         let last_root = RwLock::new(0);
 
         let slot = 1;
-        let (mut shred, coding) = Shredder::new_coding_shred_header(slot, 11, 11, 11, 11, 0);
+        let (mut shred, coding) = Shredder::new_coding_shred_header(
+            slot, 11, // index
+            11, // fec_set_index
+            11, // num_data_shreds
+            11, // num_coding_shreds
+            8,  // position
+            0,  // version
+        );
         let coding_shred =
             Shred::new_empty_from_header(shred.clone(), DataShredHeader::default(), coding.clone());
 

ledger/src/shred.rs

@@ -222,8 +222,7 @@ pub struct DataShredHeader {
 pub struct CodingShredHeader {
     pub num_data_shreds: u16,
     pub num_coding_shreds: u16,
-    #[serde(rename = "position")]
+    pub position: u16,
-    __unused: u16,
 }
 
 #[derive(Clone, Debug, PartialEq)]
@@ -382,8 +381,9 @@ impl Shred {
         slot: Slot,
         index: u32,
         fec_set_index: u32,
-        num_data: usize,
+        num_data: u16,
-        num_code: usize,
+        num_code: u16,
+        position: u16,
         version: u16,
     ) -> Self {
         let (header, coding_header) = Shredder::new_coding_shred_header(
@@ -392,6 +392,7 @@ impl Shred {
             fec_set_index,
             num_data,
             num_code,
+            position,
             version,
         );
         Shred::new_empty_from_header(header, DataShredHeader::default(), coding_header)
@@ -812,8 +813,9 @@ impl Shredder {
         slot: Slot,
         index: u32,
         fec_set_index: u32,
-        num_data: usize,
+        num_data_shreds: u16,
-        num_code: usize,
+        num_coding_shreds: u16,
+        position: u16,
         version: u16,
     ) -> (ShredCommonHeader, CodingShredHeader) {
         let header = ShredCommonHeader {
@@ -827,9 +829,9 @@ impl Shredder {
         (
             header,
             CodingShredHeader {
-                num_data_shreds: num_data as u16,
+                num_data_shreds,
-                num_coding_shreds: num_code as u16,
+                num_coding_shreds,
-                ..CodingShredHeader::default()
+                position,
             },
         )
     }
@@ -865,6 +867,8 @@ impl Shredder {
             .unwrap()
             .encode(&data, &mut parity[..])
             .unwrap();
+        let num_data = u16::try_from(num_data).unwrap();
+        let num_coding = u16::try_from(num_coding).unwrap();
         parity
             .iter()
             .enumerate()
@@ -875,6 +879,7 @@ impl Shredder {
                     fec_set_index,
                     num_data,
                     num_coding,
+                    u16::try_from(i).unwrap(), // position
                     version,
                 );
                 shred.payload[SIZE_OF_CODING_SHRED_HEADERS..].copy_from_slice(parity);
@@ -1882,7 +1887,15 @@ pub mod tests {
         );
         assert_eq!(stats.index_overrun, 4);
 
-        let shred = Shred::new_empty_coding(8, 2, 10, 30, 4, 200);
+        let shred = Shred::new_empty_coding(
+            8,   // slot
+            2,   // index
+            10,  // fec_set_index
+            30,  // num_data
+            4,   // num_code
+            1,   // position
+            200, // version
+        );
         shred.copy_to_packet(&mut packet);
         assert_eq!(
             Some((8, 2, ShredType::Code)),
@@ -1894,7 +1907,15 @@ pub mod tests {
         assert_eq!(None, get_shred_slot_index_type(&packet, &mut stats));
         assert_eq!(1, stats.index_out_of_bounds);
 
-        let (header, coding_header) = Shredder::new_coding_shred_header(8, 2, 10, 30, 4, 200);
+        let (header, coding_header) = Shredder::new_coding_shred_header(
+            8,   // slot
+            2,   // index
+            10,  // fec_set_index
+            30,  // num_data_shreds
+            4,   // num_coding_shreds
+            3,   // position
+            200, // version
+        );
         let shred = Shred::new_empty_from_header(header, DataShredHeader::default(), coding_header);
         shred.copy_to_packet(&mut packet);
         packet.data[OFFSET_OF_SHRED_TYPE] = u8::MAX;