mirror of
https://github.com/hanzoai/visor.git
synced 2026-09-24 17:04:14 +00:00
Bhasker HariharanandShentubot
3d71c627fa
The implementation is similar to linux where we track the number of bytes consumed by the application to grow the receive buffer of a given TCP endpoint. This ensures that the advertised window grows at a reasonable rate to accomodate for the sender's rate and prevents large amounts of data being held in stack buffers if the application is not actively reading or not reading fast enough. The original paper that was used to implement the linux receive buffer auto- tuning is available @ https://public.lanl.gov/radiant/pubs/drs/lacsi2001.pdf NOTE: Linux does not implement DRS as defined in that paper, it's just a good reference to understand the solution space. Updates #230 PiperOrigin-RevId: 253168283
106 lines
3.0 KiB
Go
106 lines
3.0 KiB
Go
// Copyright 2018 The gVisor Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package tcp
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import (
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"gvisor.dev/gvisor/pkg/tcpip/header"
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"gvisor.dev/gvisor/pkg/tcpip/seqnum"
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)
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const (
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// MaxSACKBlocks is the maximum number of SACK blocks stored
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// at receiver side.
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MaxSACKBlocks = 6
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)
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// UpdateSACKBlocks updates the list of SACK blocks to include the segment
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// specified by segStart->segEnd. If the segment happens to be an out of order
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// delivery then the first block in the sack.blocks always includes the
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// segment identified by segStart->segEnd.
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func UpdateSACKBlocks(sack *SACKInfo, segStart seqnum.Value, segEnd seqnum.Value, rcvNxt seqnum.Value) {
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newSB := header.SACKBlock{Start: segStart, End: segEnd}
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// Ignore any invalid SACK blocks or blocks that are before rcvNxt as
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// those bytes have already been acked.
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if newSB.End.LessThanEq(newSB.Start) || newSB.End.LessThan(rcvNxt) {
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return
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}
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if sack.NumBlocks == 0 {
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sack.Blocks[0] = newSB
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sack.NumBlocks = 1
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return
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}
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var n = 0
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for i := 0; i < sack.NumBlocks; i++ {
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start, end := sack.Blocks[i].Start, sack.Blocks[i].End
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if end.LessThanEq(rcvNxt) {
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// Discard any sack blocks that are before rcvNxt as
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// those have already been acked.
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continue
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}
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if newSB.Start.LessThanEq(end) && start.LessThanEq(newSB.End) {
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// Merge this SACK block into newSB and discard this SACK
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// block.
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if start.LessThan(newSB.Start) {
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newSB.Start = start
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}
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if newSB.End.LessThan(end) {
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newSB.End = end
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}
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} else {
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// Save this block.
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sack.Blocks[n] = sack.Blocks[i]
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n++
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}
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}
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if rcvNxt.LessThan(newSB.Start) {
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// If this was an out of order segment then make sure that the
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// first SACK block is the one that includes the segment.
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//
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// See the first bullet point in
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// https://tools.ietf.org/html/rfc2018#section-4
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if n == MaxSACKBlocks {
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// If the number of SACK blocks is equal to
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// MaxSACKBlocks then discard the last SACK block.
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n--
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}
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for i := n - 1; i >= 0; i-- {
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sack.Blocks[i+1] = sack.Blocks[i]
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}
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sack.Blocks[0] = newSB
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n++
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}
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sack.NumBlocks = n
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}
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// TrimSACKBlockList updates the sack block list by removing/modifying any block
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// where start is < rcvNxt.
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func TrimSACKBlockList(sack *SACKInfo, rcvNxt seqnum.Value) {
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n := 0
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for i := 0; i < sack.NumBlocks; i++ {
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if sack.Blocks[i].End.LessThanEq(rcvNxt) {
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continue
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}
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if sack.Blocks[i].Start.LessThan(rcvNxt) {
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// Shrink this SACK block.
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sack.Blocks[i].Start = rcvNxt
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}
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sack.Blocks[n] = sack.Blocks[i]
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n++
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}
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sack.NumBlocks = n
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}
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