New Features

• stats: Expose the effective client authority (sent on the wire as the HTTP/2 :authority header) in client stats.OutHeader events. (#9296)
  • Special Thanks: @aryansk
• metadata: Add ValueFromOutgoingContext, which reads a single metadata value from outgoing context without copying the entire outgoing metadata into a new map. (#9282)
  • Special Thanks: @yuyangguo42

Bug Fixes

• transport: Refine control buffer throttling to only count peer-induced control frames, raise the default GRPC_GO_EXPERIMENTAL_CONTROL_BUFFER_THROTTLE_LIMIT from 100 to 10,000, and close client connections if reads remain throttled for 10s. (#9563)
• server: Ensure Stop() forcefully terminates the server while GracefulStop() is waiting for active handlers to complete. (#9394)
  • Special Thanks: @stanhu
• server: Unconditionally increment the highest-seen stream ID on when handling HEADERS frames to comply with RFC 7540 §5.1.1. Previously, truncated HEADERS frames left the connection in an inconsistent state and allowed stream IDs to be reused by clients without resulting in a protocol error. (#9414)
• server: Terminate streams immediately when a HEADERS frame includes the EndStream bit. Previously, this caused server handlers to hang when reading a message. (#9391)
• server: Reject requests missing both :authority and Host headers with HTTP 400 and status Internal. (#9365)
• xds: Fix a bug where route header matchers with non-lowercase names failed to match routes. (#9353)
  • Special Thanks: @winklemad
• client: Ensure retried RPCs use the correct :authority value specified by the LB policy instead of inheriting it from a previous attempt. (#9277)
  • Special Thanks: @nvxbug
• transport: Fail streams with io.ErrUnexpectedEOF instead of io.EOF upon receiving truncated message headers or bodies after partial data has already been received. (#9204)
  • Special Thanks: @buger

Behavior Changes

• stats/otel: The grpc.lb.pick_first.* metrics have been removed and replaced with grpc.subchannel.* metrics. See gRFC A94 for more details. (#9215)

New Features

• xds: Add support for contains_match in route header matchers. (#9223)
  • Special Thanks: @nvxbug

Bug Fixes

• client: Fix a bug where a ClientConn could get permanently stuck in IDLE when an RPC was canceled during stream creation. Previously, such cancellations triggered stream cleanup twice, corrupting the channel's idleness state and causing subsequent RPCs to fail with deadline exceeded errors. (#9191)
  • Special Thanks: @utkuozdemir
• client: Fix a bug where non-gRPC HTTP responses ending with an empty DATA frame failed the RPC with status code Internal instead of preserving the HTTP-mapped status code and response body. (#9217)
  • Special Thanks: @chengxilo
• credentials: Validate metadata returned by per-RPC credentials, failing the RPC with status code Internal if invalid keys or values are found. Previously, invalid metadata from credentials was sent to the server in outgoing HTTP/2 requests. (#9202)
  • Special Thanks: @buger
• credentials/sts: Prevent potential token leakage by disallowing HTTP redirects during STS token exchange. Previously, 3xx redirects were followed automatically, replaying the request body containing authentication tokens to the redirect destination. (#9299)
  • Special Thanks: @nvxbug
• randomsubsetting: Ignore endpoints that contain no addresses. Previously, this could cause the policy to panic while computing hashes. (#9259)
  • Special Thanks: @fallintoplace
• stats/otel: Ensure method names are populated in trace spans when metrics are disabled. Previously, running with tracing enabled and metrics disabled resulted in server trace spans lacking the RPC method name (recording only "Recv."). (#9262)
• transport: Return io.ErrUnexpectedEOF when EOF is encountered after partial header or message body reads. Previously, partial reads could return a plain io.EOF, failing to distinguish truncated data from a clean end of stream. (#9204)
  • Special Thanks: @buger
• transport: Validate metadata supplied by balancers (in PickResult.Metadata) and resolver addresses, failing the RPC with status code Internal if invalid keys or values are found. Previously, invalid metadata from these sources was sent to the server in outgoing HTTP/2 requests. (#9203)
  • Special Thanks: @buger
• xds: Fix a rare corner case that could prevent a cluster from being removed when it is no longer in use. (#9140)
• xds: Fix panic during route matching for routes containing header matchers with empty exact_match strings. (#9223)
  • Special Thanks: @nvxbug
• xds: Reject routes containing header matchers with empty prefix_match or suffix_match strings. Previously, this caused a panic during route matching. (#9223)
  • Special Thanks: @nvxbug
• xds: Fix EDS drop policies being applied at a much lower rate than configured due to an integer overflow. (#9257)
  • Special Thanks: @nvxbug
• xds: Reject EDS resources containing drop policies with unsupported denominators. Previously, such resources caused the client to panic when calculating drop rates. (#9218)
  • Special Thanks: @nvxbug
• xds/rbac: Reject RBAC configurations containing nested Principal or Permission rules with :scheme or grpc- prefixed header matchers. Previously, such configurations could cause DENY policies to fail open. (#9258)
  • Special Thanks: @nvxbug
• xds/rbac: Rewrite host header matchers to :authority in nested Principal and Permission rules. Previously, this rewrite only applied to top-level rules, causing nested host matchers to never match incoming requests and DENY policies to fail open. (#9258)
  • Special Thanks: @nvxbug
• xds/rbac: Reject CidrRanges with an unset prefix length. Previously, an omitted prefix_len field caused a panic during RBAC configuration parsing. (#9250)
  • Special Thanks: @nvxbug

Performance Improvements

• transport: Avoid a heap allocation when flushing shared write buffers. (#9233)
  • Special Thanks: @zaidoon1
• credentials/alts: Support dynamic frame size negotiation and add the GRPC_GO_EXPERIMENTAL_ALTS_MAX_FRAME_SIZE environment variable (default 4KiB, max 512KiB) to configure the maximum ALTS record frame size. (#9268)

Security

• server: Reject requests missing both :authority and Host headers with HTTP 400 and status Internal. (#9365)
  • Special Thanks: @winklemad

Security

• server: Reject requests missing both :authority and Host headers with HTTP 400 and status Internal. (#9365)
  • Special Thanks: @winklemad

Security

• xds/rbac: Fix a bug where nested Principal or Permission rules with :scheme or grpc- prefixed header matchers were not rejected, which could cause DENY rules to fail open. (#9258)
  • Special Thanks: @nvxbug
• xds/rbac: Fix a bug where the host header matcher was not being replaced with :authority in nested Principal or Permission rules. (#9258)
  • Special Thanks: @nvxbug
• xds/rbac: Fix a bug where a header matcher whose name was not lowercase, such as X-Role, matched no header, which could cause DENY rules to fail open. (#9332)
  • Special Thanks: @alimony
• xds/rbac: Fix a bug where a :scheme or grpc- prefixed header matcher was accepted when its name was not lowercase. (#9332)
  • Special Thanks: @alimony
• xds/rbac: Fix a bug where a Host header matcher was not replaced with :authority. (#9332)
  • Special Thanks: @alimony

Performance

• transport: Restrict memory overhead of buffering small data frames. (#9331)

Security

• server: Stop reading from connections when flooded by HTTP/2 frames to mitigate resource exhaustion. The default value for this limit is 100 frames, excluding DATA and HEADERS, and may be changed by setting environment variable GRPC_GO_EXPERIMENTAL_CONTROL_BUFFER_THROTTLE_LIMIT.
• xds/rbac: Support Metadata and RequestedServerName permissions matcher fields. If present in a DENY rule, previously these would be ignored and fail-open.
• xds/rbac: Fix panic when parsing unsupported fields in NotRule/NotId permissions.
• xds/rbac: Support the deprecated source_ip principal identifier by treating it as equivalent to direct_remote_ip.
• xds: Fix panic when parsing route header matchers configured with empty exact_match, prefix_match, or suffix_match strings. (#9223)

New Features

• xds/googlec2p: Enable DirectPath over Interconnect support for on-premises clients via the force-xds target URI query parameter. (#9133)
• xds: Enable xDS configuration to control which fields get propagated from ORCA backend metric reports to LRS load reports. (#9145)
• authz: Add OnPolicyUpdate callback to FileWatcherOptions to notify when an authz policy is loaded or updated. (#9142)
  • Special Thanks: @hnefatl
• xds: Add support for the GCP Authentication HTTP Filter, which automatically fetches and attaches GCP Service Account Identity JWT tokens to outgoing RPCs.
  • This feature can be enabled by setting environment variable GRPC_EXPERIMENTAL_XDS_GCP_AUTHENTICATION_FILTER=true. (#9119)
• xds: Add support for xDS-based HTTP CONNECT proxies.
  • This feature can be enabled by setting environment variable GRPC_EXPERIMENTAL_XDS_HTTP_CONNECT=true. (#9151)
• xds: Add support for contains_match in route header matchers. (#9223)

Bug Fixes

• credentials/alts: Fix panic when processing malformed frames by validating that the message frame length exceeds the message type field size. (#9197)
• grpc: Fix compilation on Plan 9 targets (GOOS=plan9), broken since v1.81.0. (#9255)
  • Special Thanks: @Yusufihsangorgel

Security

• server: Stop reading from the connection when flooded by HTTP/2 frames. The default value for this limit is 100 frames, excluding DATA and HEADERS, and may be changed by setting environment variable GRPC_GO_EXPERIMENTAL_CONTROL_BUFFER_THROTTLE_LIMIT.
• xds/rbac: Support Metadata and RequestedServerName permissions matcher fields. If present in a DENY rule, previously these would be ignored and fail-open.
• xds/rbac: Fix panic when parsing unsupported fields in NotRule/NotId permissions.
• xds/rbac: Support the deprecated source_ip principal identifier by treating it as equivalent to direct_remote_ip.

Behavior Changes

• server: Remove support for GRPC_GO_EXPERIMENTAL_DISABLE_STRICT_PATH_CHECKING environment varibale. Strict incoming RPC path validation (which has been the default since v1.79.3) can no longer be disabled. (#9112)
• transport: Add environment variable to change the default max header list size from 16MB to 8KB. This may be enabled by setting GRPC_GO_EXPERIMENTAL_ENABLE_8KB_DEFAULT_HEADER_LIST_SIZE=true. This will be enabled by default in a subsequent release. (#9019)
• balancer: Load Balancing policy registry is now case-sensitive. Set GRPC_GO_EXPERIMENTAL_CASE_SENSITIVE_BALANCER_REGISTRIES=false (and file an issue) to revert to case-insensitive behavior. (#9017)

New Features

• experimental/stats: Expose a new API, NewContextWithLabelCallback, to register a callback that is invoked when telemetry labels are added. (#8877)
  • Special Thanks: @seth-epps
• client: Return a portion of the response body in the error message, when the client receives an unexpected non-gRPC HTTP response, to make debugging easier. (#8929)
  • Special Thanks: @chengxilo
• server: Add environment variable GRPC_GO_SERVER_GOROUTINE_LABELS that controls setting runtime/pprof.Labels on goroutines spawned by the server. Set GRPC_GO_SERVER_GOROUTINE_LABELS=grpc.method=true to add the grpc.method label on goroutines spawned to handle incoming requests. (#9082)
  • Special Thanks: @dfinkel

Bug Fixes

• xds/server: Fix a memory leak of HTTP filter instances occurring when route configurations are updated in-place during a Route Discovery Service (RDS) update. (#9138)
• grpc: In the deprecated gzip Compressor (used via the deprecated WithCompressor dial option), enforce the MaxRecvMsgSize limit on the decompressed message buffer, preventing excessive memory allocation from highly compressed payloads. (#9114)
  • Special Thanks: @evilgensec
• stats/opentelemetry: Record retry attempts, grpc.previous-rpc-attempts, at the call level and not the attempt level. (#8923)
• encoding: Ensure Close() is always called on readers returned from Compressor.Decompress if possible. (#9135)
• channelz: Fix the LastMessageSentTimestamp and LastMessageReceivedTimestamp fields in SocketMetrics to ensure they contain correct timestamp values. (#9109)

Security

• xds/rbac: Fix a potential authorization bypass caused by incorrectly falling through URI/DNS SANs to Subject Distinguished Name (DN) when matching the authenticated principal name. With this fix, only the first non-empty identity source will be used, as per gRFC A41. (#9111)
  • Special Thanks: @al4an444

Bug Fixes

• otel: Segregate client and server RPC information used for metrics and traces, to avoid one overwriting the other. (#9081)

Dependencies

• Upgrade dependencies to latest.