From d474e7a2b0ee99d75cd9afbab8ba0b61fda2fb76 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Em=C3=ADdio=20Neto?=
 <9735060+emdneto@users.noreply.github.com>
Date: Mon, 24 Jun 2024 13:26:20 -0300
Subject: [PATCH] Validate links at span creation (#3991)

---
 CHANGELOG.md                                  |  4 ++-
 .../src/opentelemetry/sdk/trace/__init__.py   | 29 +++++++++++--------
 opentelemetry-sdk/tests/trace/test_trace.py   | 25 ++++++++++++++++
 3 files changed, 45 insertions(+), 13 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 32698e9436..510c9bf630 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -24,8 +24,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   ([#3973](https://github.com/open-telemetry/opentelemetry-python/pull/3966))
 - Update semantic conventions to version 1.26.0.
   ([#3964](https://github.com/open-telemetry/opentelemetry-python/pull/3964))
-  - Use semconv exception attributes for record exceptions in spans
+- Use semconv exception attributes for record exceptions in spans
   ([#3979](https://github.com/open-telemetry/opentelemetry-python/pull/3979))
+- Validate links at span creation
+  ([#3991](https://github.com/open-telemetry/opentelemetry-python/pull/3991))
 
 ## Version 1.25.0/0.46b0 (2024-05-30)
 
diff --git a/opentelemetry-sdk/src/opentelemetry/sdk/trace/__init__.py b/opentelemetry-sdk/src/opentelemetry/sdk/trace/__init__.py
index 97fb843f6f..a7094b547c 100644
--- a/opentelemetry-sdk/src/opentelemetry/sdk/trace/__init__.py
+++ b/opentelemetry-sdk/src/opentelemetry/sdk/trace/__init__.py
@@ -816,16 +816,7 @@ def __init__(
                 )
                 self._events.append(event)
 
-        if links is None:
-            self._links = self._new_links()
-        else:
-            for link in links:
-                link._attributes = BoundedAttributes(
-                    self._limits.max_link_attributes,
-                    link.attributes,
-                    max_value_len=self._limits.max_attribute_length,
-                )
-            self._links = BoundedList.from_seq(self._limits.max_links, links)
+        self._links = self._new_links(links)
 
     def __repr__(self):
         return f'{type(self).__name__}(name="{self._name}", context={self._context})'
@@ -833,8 +824,22 @@ def __repr__(self):
     def _new_events(self):
         return BoundedList(self._limits.max_events)
 
-    def _new_links(self):
-        return BoundedList(self._limits.max_links)
+    def _new_links(self, links: Sequence[trace_api.Link]):
+        if not links:
+            return BoundedList(self._limits.max_links)
+
+        valid_links = []
+        for link in links:
+            if link and _is_valid_link(link.context, link.attributes):
+                # pylint: disable=protected-access
+                link._attributes = BoundedAttributes(
+                    self._limits.max_link_attributes,
+                    link.attributes,
+                    max_value_len=self._limits.max_attribute_length,
+                )
+                valid_links.append(link)
+
+        return BoundedList.from_seq(self._limits.max_links, valid_links)
 
     def get_span_context(self):
         return self._context
diff --git a/opentelemetry-sdk/tests/trace/test_trace.py b/opentelemetry-sdk/tests/trace/test_trace.py
index 07db25474f..9f37564309 100644
--- a/opentelemetry-sdk/tests/trace/test_trace.py
+++ b/opentelemetry-sdk/tests/trace/test_trace.py
@@ -954,14 +954,29 @@ def test_add_link_with_invalid_span_context(self):
             root.add_link(None)
             self.assertEqual(len(root.links), 0)
 
+        with self.tracer.start_as_current_span(
+            "root", links=[trace_api.Link(other_context), None]
+        ) as root:
+            self.assertEqual(len(root.links), 0)
+
     def test_add_link_with_invalid_span_context_with_attributes(self):
         invalid_context = trace_api.INVALID_SPAN_CONTEXT
 
         with self.tracer.start_as_current_span("root") as root:
+            root.add_link(invalid_context)
             root.add_link(invalid_context, {"name": "neighbor"})
             self.assertEqual(len(root.links), 1)
             self.assertEqual(root.links[0].attributes, {"name": "neighbor"})
 
+        with self.tracer.start_as_current_span(
+            "root",
+            links=[
+                trace_api.Link(invalid_context, {"name": "neighbor"}),
+                trace_api.Link(invalid_context),
+            ],
+        ) as root:
+            self.assertEqual(len(root.links), 1)
+
     def test_add_link_with_invalid_span_context_with_tracestate(self):
         invalid_context = trace.SpanContext(
             trace_api.INVALID_TRACE_ID,
@@ -972,9 +987,19 @@ def test_add_link_with_invalid_span_context_with_tracestate(self):
 
         with self.tracer.start_as_current_span("root") as root:
             root.add_link(invalid_context)
+            root.add_link(trace_api.INVALID_SPAN_CONTEXT)
             self.assertEqual(len(root.links), 1)
             self.assertEqual(root.links[0].context.trace_state, "foo=bar")
 
+        with self.tracer.start_as_current_span(
+            "root",
+            links=[
+                trace_api.Link(invalid_context),
+                trace_api.Link(trace_api.INVALID_SPAN_CONTEXT),
+            ],
+        ) as root:
+            self.assertEqual(len(root.links), 1)
+
     def test_update_name(self):
         with self.tracer.start_as_current_span("root") as root:
             # name