Add TCP BBR setup script with README and LICENSE

Bash script to automatically enable TCP BBR congestion control on Linux servers. Supports Debian/Ubuntu/CentOS/RHEL/Alpine/Arch, includes --check and --dry-run modes, sysctl backup, and verification. Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
2026-01-31 14:56:07 +03:00
commit a206c04ba9
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+MIT License
+
+Copyright (c) 2026 bbr-setup contributors
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
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+# bbr-setup
+
+Bash script that enables [TCP BBR](https://github.com/google/bbr) congestion control on Linux servers with a single command.
+
+## Quick start
+
+```bash
+curl -fsSL https://raw.githubusercontent.com/user/bbr-setup/main/setup.sh | sudo bash
+```
+
+Or clone and run locally:
+
+```bash
+git clone https://github.com/user/bbr-setup.git
+cd bbr-setup
+sudo bash setup.sh
+```
+
+## What it does
+
+1. Verifies root permissions, distro, and kernel version (4.9+ required)
+2. Checks that the `tcp_bbr` module is available
+3. Backs up existing sysctl configuration
+4. Writes BBR parameters to `/etc/sysctl.d/99-bbr.conf` (or `/etc/sysctl.conf` as fallback)
+5. Applies and verifies the new settings
+
+Parameters applied:
+
+```
+net.core.default_qdisc = fq
+net.ipv4.tcp_congestion_control = bbr
+```
+
+## Usage
+
+```
+bbr-setup 1.0.0 — enable TCP BBR congestion control
+
+Usage: setup.sh [OPTIONS]
+
+Options:
+  --check      Show current BBR status and exit
+  --dry-run    Show what would be done without making changes
+  -h, --help   Show this help message
+  -v, --version  Show version
+```
+
+### Examples
+
+Apply BBR:
+
+```bash
+sudo bash setup.sh
+```
+
+Check current status without changing anything:
+
+```bash
+sudo bash setup.sh --check
+```
+
+Preview what would be changed:
+
+```bash
+sudo bash setup.sh --dry-run
+```
+
+## Supported distributions
+
+- Debian / Ubuntu
+- CentOS / RHEL / Fedora
+- Alpine Linux
+- Arch Linux
+- Any Linux with kernel 4.9+ and the `tcp_bbr` module
+
+## Exit codes
+
+| Code | Meaning |
+|------|---------|
+| `0`  | Success or BBR already enabled |
+| `1`  | Error (missing root, old kernel, module unavailable, verification failed) |
+
+## License
+
+[MIT](LICENSE)
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+#!/usr/bin/env bash
+set -euo pipefail
+
+# ---------------------------------------------------------------------------
+#  TCP BBR Setup Script
+#  Automatically enables BBR congestion control on Linux servers.
+# ---------------------------------------------------------------------------
+
+readonly VERSION="1.0.0"
+readonly SYSCTL_DROP="/etc/sysctl.d/99-bbr.conf"
+readonly SYSCTL_MAIN="/etc/sysctl.conf"
+readonly MIN_KERNEL_MAJOR=4
+readonly MIN_KERNEL_MINOR=9
+
+# ── Modes ──────────────────────────────────────────────────────────────────
+DRY_RUN=false
+CHECK_ONLY=false
+
+# ── Colors ─────────────────────────────────────────────────────────────────
+if [[ -t 1 ]]; then
+    RED='\033[0;31m'
+    GREEN='\033[0;32m'
+    YELLOW='\033[0;33m'
+    CYAN='\033[0;36m'
+    BOLD='\033[1m'
+    RESET='\033[0m'
+else
+    RED='' GREEN='' YELLOW='' CYAN='' BOLD='' RESET=''
+fi
+
+# ── Logging ────────────────────────────────────────────────────────────────
+_ts() { date '+%H:%M:%S'; }
+
+log_info()  { printf "${GREEN}[%s] [INFO]${RESET}  %s\n"  "$(_ts)" "$*"; }
+log_warn()  { printf "${YELLOW}[%s] [WARN]${RESET}  %s\n" "$(_ts)" "$*"; }
+log_error() { printf "${RED}[%s] [ERROR]${RESET} %s\n"    "$(_ts)" "$*" >&2; }
+
+die() { log_error "$*"; exit 1; }
+
+# ── Usage ──────────────────────────────────────────────────────────────────
+usage() {
+    cat <<EOF
+${BOLD}bbr-setup ${VERSION}${RESET} — enable TCP BBR congestion control
+
+Usage: $(basename "$0") [OPTIONS]
+
+Options:
+  --check      Show current BBR status and exit
+  --dry-run    Show what would be done without making changes
+  -h, --help   Show this help message
+  -v, --version  Show version
+
+Examples:
+  sudo bash setup.sh              # apply BBR
+  sudo bash setup.sh --check      # status only
+  sudo bash setup.sh --dry-run    # preview changes
+EOF
+    exit 0
+}
+
+# ── Argument parsing ───────────────────────────────────────────────────────
+parse_args() {
+    while [[ $# -gt 0 ]]; do
+        case "$1" in
+            --check)     CHECK_ONLY=true ;;
+            --dry-run)   DRY_RUN=true ;;
+            -h|--help)   usage ;;
+            -v|--version) echo "bbr-setup ${VERSION}"; exit 0 ;;
+            *) die "Unknown option: $1. Use --help for usage." ;;
+        esac
+        shift
+    done
+}
+
+# ── Detect distro ─────────────────────────────────────────────────────────
+detect_distro() {
+    local distro="unknown"
+    if   [[ -f /etc/os-release ]]; then
+        # shellcheck disable=SC1091
+        . /etc/os-release
+        distro="${ID}"
+    elif [[ -f /etc/redhat-release ]]; then
+        distro="rhel"
+    elif [[ -f /etc/alpine-release ]]; then
+        distro="alpine"
+    fi
+    echo "${distro}"
+}
+
+# ── Kernel version check ─────────────────────────────────────────────────
+check_kernel() {
+    local kver
+    kver=$(uname -r)
+    local major minor
+    major=$(echo "$kver" | cut -d. -f1)
+    minor=$(echo "$kver" | cut -d. -f2)
+
+    log_info "Kernel version: ${kver}"
+
+    if (( major > MIN_KERNEL_MAJOR )) || { (( major == MIN_KERNEL_MAJOR )) && (( minor >= MIN_KERNEL_MINOR )); }; then
+        log_info "Kernel ${kver} meets minimum requirement (${MIN_KERNEL_MAJOR}.${MIN_KERNEL_MINOR}+)"
+    else
+        die "Kernel ${kver} is too old. BBR requires ${MIN_KERNEL_MAJOR}.${MIN_KERNEL_MINOR}+"
+    fi
+}
+
+# ── Check BBR module availability ─────────────────────────────────────────
+check_bbr_module() {
+    if lsmod | grep -q tcp_bbr; then
+        log_info "Module tcp_bbr is loaded"
+        return 0
+    fi
+
+    if modprobe -n tcp_bbr 2>/dev/null; then
+        log_info "Module tcp_bbr is available (not yet loaded)"
+        return 0
+    fi
+
+    # On newer kernels BBR can be built-in (not a module)
+    if [[ -f /proc/config.gz ]]; then
+        if zcat /proc/config.gz 2>/dev/null | grep -q 'CONFIG_TCP_CONG_BBR=y'; then
+            log_info "BBR is built into the kernel"
+            return 0
+        fi
+    fi
+
+    if sysctl net.ipv4.tcp_available_congestion_control 2>/dev/null | grep -q bbr; then
+        log_info "BBR is listed as available congestion control"
+        return 0
+    fi
+
+    die "tcp_bbr module is not available on this system"
+}
+
+# ── Read current state ────────────────────────────────────────────────────
+get_current_cc()    { sysctl -n net.ipv4.tcp_congestion_control 2>/dev/null || echo "unknown"; }
+get_current_qdisc() { sysctl -n net.core.default_qdisc 2>/dev/null           || echo "unknown"; }
+
+show_status() {
+    local cc qdisc
+    cc=$(get_current_cc)
+    qdisc=$(get_current_qdisc)
+
+    log_info "Current congestion control : ${BOLD}${cc}${RESET}"
+    log_info "Current default qdisc      : ${BOLD}${qdisc}${RESET}"
+
+    if [[ "$cc" == "bbr" && ( "$qdisc" == "fq" || "$qdisc" == "fq_codel" ) ]]; then
+        return 0  # already configured
+    fi
+    return 1      # needs configuration
+}
+
+# ── Determine sysctl target file ─────────────────────────────────────────
+pick_sysctl_file() {
+    if [[ -d /etc/sysctl.d ]]; then
+        echo "${SYSCTL_DROP}"
+    else
+        echo "${SYSCTL_MAIN}"
+    fi
+}
+
+# ── Backup ────────────────────────────────────────────────────────────────
+backup_sysctl() {
+    local target="$1"
+    if [[ -f "$target" ]]; then
+        local bak="${target}.bak.$(date '+%Y%m%d_%H%M%S')"
+        cp -a "$target" "$bak"
+        log_info "Backup created: ${bak}"
+        echo "$bak"
+    fi
+}
+
+# ── Write sysctl parameters ──────────────────────────────────────────────
+write_params() {
+    local target="$1"
+    local needs_cc=true
+    local needs_qdisc=true
+
+    if [[ -f "$target" ]]; then
+        grep -q '^net.core.default_qdisc\s*=\s*fq'  "$target" && needs_qdisc=false
+        grep -q '^net.ipv4.tcp_congestion_control\s*=\s*bbr' "$target" && needs_cc=false
+    fi
+
+    # Also check the main sysctl.conf if we're writing to a drop-in
+    if [[ "$target" != "$SYSCTL_MAIN" && -f "$SYSCTL_MAIN" ]]; then
+        grep -q '^net.core.default_qdisc\s*=\s*fq'  "$SYSCTL_MAIN" && needs_qdisc=false
+        grep -q '^net.ipv4.tcp_congestion_control\s*=\s*bbr' "$SYSCTL_MAIN" && needs_cc=false
+    fi
+
+    if ! $needs_cc && ! $needs_qdisc; then
+        log_info "Parameters already present in ${target}"
+        return 0
+    fi
+
+    {
+        echo ""
+        echo "# TCP BBR — added by bbr-setup ${VERSION} on $(date '+%Y-%m-%d %H:%M:%S')"
+        $needs_qdisc && echo "net.core.default_qdisc = fq"
+        $needs_cc    && echo "net.ipv4.tcp_congestion_control = bbr"
+    } >> "$target"
+
+    log_info "Parameters written to ${target}"
+}
+
+# ── Apply & verify ────────────────────────────────────────────────────────
+apply_sysctl() {
+    local target="$1"
+
+    # Load the bbr module if it isn't loaded yet
+    if ! lsmod | grep -q tcp_bbr; then
+        modprobe tcp_bbr 2>/dev/null || true
+    fi
+
+    sysctl -p "$target" >/dev/null 2>&1
+
+    # Also reload main if we used a drop-in
+    if [[ "$target" != "$SYSCTL_MAIN" && -f "$SYSCTL_MAIN" ]]; then
+        sysctl -p "$SYSCTL_MAIN" >/dev/null 2>&1 || true
+    fi
+
+    local new_cc new_qdisc
+    new_cc=$(get_current_cc)
+    new_qdisc=$(get_current_qdisc)
+
+    if [[ "$new_cc" == "bbr" ]]; then
+        log_info "Verification passed: congestion control = ${BOLD}${new_cc}${RESET}"
+    else
+        die "Verification failed: congestion control is '${new_cc}', expected 'bbr'"
+    fi
+
+    if [[ "$new_qdisc" == "fq" || "$new_qdisc" == "fq_codel" ]]; then
+        log_info "Verification passed: default qdisc = ${BOLD}${new_qdisc}${RESET}"
+    else
+        log_warn "Qdisc is '${new_qdisc}' (expected 'fq'). This may still work but fq is recommended."
+    fi
+}
+
+# ── Summary ───────────────────────────────────────────────────────────────
+print_summary() {
+    local old_cc="$1" old_qdisc="$2" new_cc="$3" new_qdisc="$4" backup_path="${5:-}"
+
+    echo ""
+    printf "${BOLD}%-30s  %-14s  %-14s${RESET}\n" "" "Before" "After"
+    printf "%-30s  %-14s  %-14s\n" "Congestion control" "$old_cc" "$new_cc"
+    printf "%-30s  %-14s  %-14s\n" "Default qdisc" "$old_qdisc" "$new_qdisc"
+    echo ""
+
+    if [[ -n "$backup_path" ]]; then
+        log_info "Backup saved to: ${backup_path}"
+    fi
+}
+
+# ══════════════════════════════════════════════════════════════════════════
+#  Main
+# ══════════════════════════════════════════════════════════════════════════
+main() {
+    parse_args "$@"
+
+    echo ""
+    printf "${CYAN}${BOLD}  TCP BBR Setup ${VERSION}${RESET}\n"
+    echo ""
+
+    # ── Root check ─────────────────────────────────────────────────────
+    if [[ $EUID -ne 0 ]]; then
+        die "This script must be run as root (use sudo)"
+    fi
+
+    # ── Distro detection ───────────────────────────────────────────────
+    local distro
+    distro=$(detect_distro)
+    log_info "Detected distro: ${BOLD}${distro}${RESET}"
+
+    # ── Kernel check ───────────────────────────────────────────────────
+    check_kernel
+
+    # ── BBR module check ───────────────────────────────────────────────
+    check_bbr_module
+
+    # ── Current state ──────────────────────────────────────────────────
+    local old_cc old_qdisc
+    old_cc=$(get_current_cc)
+    old_qdisc=$(get_current_qdisc)
+
+    if show_status; then
+        log_info "${GREEN}BBR is already enabled. Nothing to do.${RESET}"
+        print_summary "$old_cc" "$old_qdisc" "$old_cc" "$old_qdisc"
+        exit 0
+    fi
+
+    # ── Check-only mode ────────────────────────────────────────────────
+    if $CHECK_ONLY; then
+        log_warn "BBR is NOT currently enabled"
+        exit 1
+    fi
+
+    # ── Dry-run mode ───────────────────────────────────────────────────
+    local target
+    target=$(pick_sysctl_file)
+
+    if $DRY_RUN; then
+        log_warn "Dry-run mode — no changes will be made"
+        echo ""
+        log_info "Would write to: ${target}"
+        log_info "Parameters:"
+        echo "  net.core.default_qdisc = fq"
+        echo "  net.ipv4.tcp_congestion_control = bbr"
+        echo ""
+        exit 0
+    fi
+
+    # ── Apply changes ──────────────────────────────────────────────────
+    log_info "Configuring BBR..."
+
+    local backup_path=""
+    backup_path=$(backup_sysctl "$target")
+
+    write_params "$target"
+    apply_sysctl "$target"
+
+    local new_cc new_qdisc
+    new_cc=$(get_current_cc)
+    new_qdisc=$(get_current_qdisc)
+
+    print_summary "$old_cc" "$old_qdisc" "$new_cc" "$new_qdisc" "$backup_path"
+    log_info "${GREEN}${BOLD}Done.${RESET}"
+}
+
+main "$@"