Apply suggestions from @jtraglia

specs/_features/eip7594/das-core.md

@@ -8,6 +8,8 @@
 <!-- START doctoc generated TOC please keep comment here to allow auto update -->
 <!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
 
+- [Constants](#constants)
+  - [Misc](#misc)
 - [Custom types](#custom-types)
 - [Configuration](#configuration)
   - [Data size](#data-size)
@@ -39,6 +41,16 @@
 <!-- END doctoc generated TOC please keep comment here to allow auto update -->
 <!-- /TOC -->
 
+## Constants
+
+The following values are (non-configurable) constants used throughout the specification.
+
+### Misc
+
+| Name | Value |
+| - | - |
+| `UINT256_MAX` | `uint256(2**256 - 1)` |
+
 ## Custom types
 
 We define the following Python custom types for type hinting and readability:
@@ -95,8 +107,11 @@ def get_custody_columns(node_id: NodeID, custody_subnet_count: uint64) -> Sequen
     subnet_ids = []
     i = 0
     while len(subnet_ids) < custody_subnet_count:
+        if node_id == UINT256_MAX:
+            node_id = 0
+
         subnet_id = (
-            bytes_to_uint64(hash(uint_to_bytes(uint64(node_id + i)))[0:8])
+            bytes_to_uint64(hash(uint_to_bytes(uint256(node_id + i)))[0:8])
             % DATA_COLUMN_SIDECAR_SUBNET_COUNT
         )
         if subnet_id not in subnet_ids:

tests/core/pyspec/eth2spec/test/eip7594/networking/test_get_custody_columns.py

@@ -7,9 +7,12 @@ from eth2spec.test.context import (
 )
 
 
-def _run_get_custody_columns(spec, rng):
-    node_id = rng.randint(0, 2**32 - 1)
-    custody_subnet_count = rng.randint(0, spec.config.DATA_COLUMN_SIDECAR_SUBNET_COUNT)
+def _run_get_custody_columns(spec, rng, node_id=None, custody_subnet_count=None):
+    if node_id is None:
+        node_id = rng.randint(0, 2**256 - 1)
+
+    if custody_subnet_count is None:
+        custody_subnet_count = rng.randint(0, spec.config.DATA_COLUMN_SIDECAR_SUBNET_COUNT)
 
     result = spec.get_custody_columns(node_id, custody_subnet_count)
     yield 'node_id', 'meta', node_id
@@ -25,6 +28,43 @@ def _run_get_custody_columns(spec, rng):
     yield 'result', 'meta', python_list_result
 
 
+@with_eip7594_and_later
+@spec_test
+@single_phase
+def test_get_custody_columns__min_node_id_min_custody_subnet_count(spec):
+    rng = random.Random(1111)
+    yield from _run_get_custody_columns(spec, rng, node_id=0, custody_subnet_count=0)
+
+
+@with_eip7594_and_later
+@spec_test
+@single_phase
+def test_get_custody_columns__min_node_id_max_custody_subnet_count(spec):
+    rng = random.Random(1111)
+    yield from _run_get_custody_columns(
+        spec, rng, node_id=0,
+        custody_subnet_count=spec.config.DATA_COLUMN_SIDECAR_SUBNET_COUNT)
+
+
+@with_eip7594_and_later
+@spec_test
+@single_phase
+def test_get_custody_columns__max_node_id_min_custody_subnet_count(spec):
+    rng = random.Random(1111)
+    yield from _run_get_custody_columns(spec, rng, node_id=2**256 - 1, custody_subnet_count=0)
+
+
+@with_eip7594_and_later
+@spec_test
+@single_phase
+def test_get_custody_columns__max_node_id_max_custody_subnet_count(spec):
+    rng = random.Random(1111)
+    yield from _run_get_custody_columns(
+        spec, rng, node_id=2**256 - 1,
+        custody_subnet_count=spec.config.DATA_COLUMN_SIDECAR_SUBNET_COUNT,
+    )
+
+
 @with_eip7594_and_later
 @spec_test
 @single_phase