unslop some comments

iputil/packet_test.go

@@ -180,13 +180,8 @@ func Test_CreateRejectPacket_NoICMPError(t *testing.T) {
 	}
 }
 
-// Test_CreateRejectPacket_RespectsCap guards against H2: with UDP GRO the
-// scratch buffer reused to build a reject is a single coalesced segment inside
-// a shared recvmmsg row. Its length covers just that segment, but an uncapped
-// slice's capacity runs on into the next, not-yet-processed segment. Because
-// CreateRejectPacket honors cap, capping the borrowed segment to its own length
-// (cap==len) makes it physically impossible for an oversized ICMPv6 reject to
-// overwrite the neighbor segment's bytes.
+// Test_CreateRejectPacket_RespectsCap ensures it is impossible for
+// an oversized ICMPv6 reject to overwrite the neighbor segment's bytes.
 func Test_CreateRejectPacket_RespectsCap(t *testing.T) {
 	src := net.ParseIP("fd00::1")
 	dst := net.ParseIP("fd00::2")

overlay/batch/batch.go

@@ -7,9 +7,9 @@ type RxBatcher interface {
 	Reserve(sz int) []byte
 	// Commit borrows pkt. The caller must keep pkt valid until the next Flush
 	Commit(pkt []byte) error
-	// Flush emits every queued packet in arrival order. Returns the
-	// first error observed; keeps draining so one bad packet doesn't hold up
-	// the rest. After Flush returns, borrowed payload slices may be recycled.
+	// Flush emits every queued packet in arrival order.
+	// Returns the first error observed; keeps draining so one bad packet doesn't hold up the rest.
+	// After Flush returns, borrowed payload slices may be recycled.
 	Flush() error
 }
 
@@ -21,8 +21,8 @@ type TxBatcher interface {
 	// caller must keep pkt valid until the next Flush. Pass 0 (Not-ECT)
 	// to leave the outer ECN field unset.
 	Commit(pkt []byte, dst netip.AddrPort, outerECN byte)
-	// Flush emits every queued packet via the underlying batch writer in
-	// arrival order. Returns an errors.Join of one or more errors. After Flush returns,
-	// borrowed payload slices may be recycled.
+	// Flush emits every queued packet via the underlying batch writer in arrival order.
+	// Returns an errors.Join of one or more errors.
+	// After Flush returns, borrowed payload slices may be recycled.
 	Flush() error
 }

overlay/batch/coalesce_core.go

@@ -140,14 +140,7 @@ func ipHeadersMatch(a, b []byte, isV6 bool) bool {
 }
 
 // Arena is an injectable byte-slab that hands out non-overlapping borrowed
-// slices via Reserve and releases them in bulk via Reset. Coalescers take
-// an *Arena at construction so the caller controls the slab lifetime and
-// can share one slab across multiple coalescers (MultiCoalescer hands the
-// same *Arena to every lane so the lanes don't carry their own backings).
-//
-// Reserve borrows; the slice is valid until the next Reset. The slab grows
-// (by allocating a fresh, larger backing array) if a Reserve doesn't fit;
-// pre-size the arena via NewArena to avoid that path on the hot path.
+// slices via Reserve and releases them in bulk via Reset.
 type Arena struct {
 	buf []byte
 }

overlay/batch/multi_coalesce.go

@@ -110,9 +110,8 @@ func (m *MultiCoalescer) Commit(pkt []byte) error {
 	return m.pt.Commit(pkt)
 }
 
-// Flush drains every lane in a fixed order — TCP, UDP, passthrough — then
-// resets the shared arena once. A lane error doesn't stop the remaining
-// lanes; the joined errors are returned.
+// Flush drains every lane in a fixed order, then resets the shared arena once.
+// A lane error doesn't stop the remaining lanes; the joined errors are returned.
 func (m *MultiCoalescer) Flush() error {
 	var errs []error
 	if m.tcp != nil {

overlay/batch/tcp_coalesce.go

@@ -12,10 +12,7 @@ import (
 	"github.com/slackhq/nebula/overlay/tio"
 )
 
-// ipProtoTCP is the IANA protocol number for TCP. Hardcoded instead of
-// reaching for golang.org/x/sys/unix — that package doesn't define the
-// constant on Windows, which would break cross-compiles even though this
-// file runs unchanged on every platform.
+// ipProtoTCP is the IANA protocol number for TCP. Defined here to help Windows out.
 const ipProtoTCP = 6
 
 // tcpCoalesceBufSize caps total bytes per superpacket. Mirrors the kernel's
@@ -23,8 +20,7 @@ const ipProtoTCP = 6
 const tcpCoalesceBufSize = 65535
 
 // tcpCoalesceMaxSegs caps how many segments we'll coalesce into a single
-// superpacket. Keeping this well below the kernel's TSO ceiling bounds
-// latency.
+// superpacket. Keeping this well below the kernel's TSO ceiling bounds latency.
 const tcpCoalesceMaxSegs = 64
 
 // tcpCoalesceHdrCap is the scratch space we copy a seed's IP+TCP header
@@ -118,8 +114,8 @@ type parsedTCP struct {
 
 // parseTCPBase extracts the flow key and IP/TCP offsets for any TCP packet,
 // regardless of whether it's admissible for coalescing. Returns ok=false
-// for non-TCP or malformed input. Accepts IPv4 (no options, no fragmentation)
-// and IPv6 (no extension headers).
+// for non-TCP or malformed input.
+// Accepts IPv4 (no options or fragmentation) and IPv6 (no extension headers).
 func parseTCPBase(pkt []byte) (parsedTCP, bool) {
 	var p parsedTCP
 	ip, ok := parseIPPrologue(pkt, ipProtoTCP)
@@ -178,9 +174,7 @@ func (c *TCPCoalescer) Reserve(sz int) []byte {
 	return c.reserver(sz)
 }
 
-// Commit borrows pkt. The caller must keep pkt valid until the next Flush,
-// whether or not the packet was coalesced — passthrough (non-admissible)
-// packets are queued and written at Flush time, not synchronously.
+// Commit borrows pkt. The caller must keep pkt valid until the next Flush.
 func (c *TCPCoalescer) Commit(pkt []byte) error {
 	if c.gsoW == nil {
 		c.addPassthrough(pkt)
@@ -246,15 +240,7 @@ func (c *TCPCoalescer) commitParsed(pkt []byte, info parsedTCP) error {
 	return nil
 }
 
-// Flush emits every queued event in (per-flow) seq order. Coalesced slots
-// go out via WriteGSO; passthrough slots go out via plainW.Write.
-// reorderForFlush first sorts each flow's slots into TCP-seq order within
-// passthrough-bounded segments and merges contiguous adjacent slots, so
-// any wire-side reorder that crossed an rxOrder batch boundary doesn't
-// get amplified into kernel-visible reorder by the slot machinery.
-// Returns the first error observed; keeps draining so one bad packet
-// doesn't hold up the rest. After Flush returns, borrowed payload slices
-// may be recycled.
+// Flush emits every queued event in (per-flow) seq order.
 func (c *TCPCoalescer) Flush() error {
 	first := c.drain()
 	if c.resetter != nil {
@@ -328,8 +314,7 @@ func (c *TCPCoalescer) seed(pkt []byte, info parsedTCP) {
 }
 
 // canAppend reports whether info's packet extends the slot's seed: same
-// header shape and stable contents, adjacent seq, not oversized, chain not
-// closed.
+// header shape and stable contents, adjacent seq, not oversized, chain not closed.
 func (c *TCPCoalescer) canAppend(s *coalesceSlot, pkt []byte, info parsedTCP) bool {
 	if s.psh {
 		return false
@@ -397,8 +382,7 @@ func (c *TCPCoalescer) release(s *coalesceSlot) {
 	c.pool = append(c.pool, s)
 }
 
-// flushSlot patches the header and calls WriteGSO. Does not remove the
-// slot from c.slots.
+// flushSlot patches the header and calls WriteGSO. Does not remove the slot from c.slots.
 func (c *TCPCoalescer) flushSlot(s *coalesceSlot) error {
 	total := s.hdrLen + s.totalPay
 	l4Len := total - s.ipHdrLen
@@ -427,9 +411,7 @@ func (c *TCPCoalescer) flushSlot(s *coalesceSlot) error {
 
 // headersMatch compares two IP+TCP header prefixes for byte-for-byte
 // equality on every field that must be identical across coalesced
-// segments. Size/IPID/IPCsum/seq/flags/tcpCsum are masked out. The IP-level
-// ECN codepoint is compared (via ipHeadersMatch) so segments with differing
-// ECN don't coalesce, matching kernel GRO.
+// segments. Size/IPID/IPCsum/seq/flags/tcpCsum are masked out.
 func headersMatch(a, b []byte, isV6 bool, ipHdrLen int) bool {
 	if len(a) != len(b) {
 		return false

overlay/batch/udp_coalesce.go

@@ -22,10 +22,7 @@ const udpCoalesceMaxSegs = 64
 // into. IPv6 (40) + UDP (8) = 48; round up for safety.
 const udpCoalesceHdrCap = 64
 
-// udpSlot is one entry in the UDPCoalescer's ordered event queue. Same
-// passthrough-vs-coalesced shape as the TCP coalescer's slot, but no
-// seq/PSH/CWR bookkeeping — UDP segments only need 5-tuple + length
-// matching to coalesce.
+// udpSlot is one entry in the UDPCoalescer's ordered event queue.
 type udpSlot struct {
 	passthrough bool
 	rawPkt      []byte // borrowed when passthrough

overlay/tio/blockon_linux.go

@@ -12,15 +12,10 @@ import (
 // blockOn parks the calling goroutine until fd is ready (events is POLLIN for
 // reads, POLLOUT for writes) or shutdownFd signals teardown. It builds the
 // pollfd array on the stack every call, so concurrent callers on the same
-// Queue never share Revents storage: the previous shared-array implementation
-// was a genuine Go data race when two writers parked in poll(2) at once (the
-// kernel writing Revents while another goroutine zeroed it). Level-triggered
-// events kept it from deadlocking, but it was still a race.
+// Queue never share Revents storage.
 //
-// Poll(2) is looped over EINTR. err is checked before the Revents bits are
-// trusted, since a failed poll may leave them bogus. Returns os.ErrClosed when
-// shutdown was signaled (POLLIN on shutdownFd) or either fd reported a problem
-// condition (POLLHUP|POLLNVAL|POLLERR).
+// Returns os.ErrClosed when shutdown was signaled (POLLIN on shutdownFd)
+// or either fd reported a problem condition (POLLHUP|POLLNVAL|POLLERR).
 func blockOn(fd, shutdownFd int32, events int16) error {
 	const problemFlags = unix.POLLHUP | unix.POLLNVAL | unix.POLLERR
 	pfds := [2]unix.PollFd{