BBRv3 kernel compilation on Linux machines

README.md

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+# BBRv3 installation guide for Linux machines
+
+Official GitHub BBRv3 repository: https://github.com/google/bbr/blob/v3/README.md
+
+Install the necessary libraries
+```
+$ yum update -y
+$ yum groupinstall 'Development Tools' -y
+$ yum install elfutils-libelf-devel bison flex openssl-devel openssl ncurses-devel zstd iperf3 wget net-tools nano bc kernel-devel epel-release kernel-modules-extra kernel-debug-modules-extra -y
+$ yum install xz-lzma-compat rng-tools lvm2 iscsi-initiator-utils cifs-utils biosdevname nvme-cli plymouth cryptsetup lldpad mdadm nbd -y
+```
+
+Get the kernel sources for TCP BBRv3 from GitHub repository
+```
+$ git clone -o google-bbr -b v3  https://github.com/google/bbr.git
+$ cd bbr
+```
+
+Create ssh key
+```
+$ ssh-keygen
+$ cat ~/.ssh/id_rsa.pub >> ~/.ssh/authorized_keys
+$ ssh localhost
+$ exit
+```
+
+Merge Linux config to build the kernel. NOTE: this is needed to boot into the new kernel.
+```
+$ ls -la /boot/config-$(uname -r)
+# In this case, my output is: /boot/config-4.18.0-477.21.1.el8_8.x86_64
+$ cp /boot/config-4.18.0-477.21.1.el8_8.x86_64 ~/bbr/
+```
+
+Modify the `gce-install.sh` file to merge the Linux config with the TCP BBRv3
+```
+$ sed -i 's/INSTALL_MOD_PATH=${GCE_INSTALL_DIR}/INSTALL_MOD_PATH=${GCE_INSTALL_DIR} \\\n           INSTALL_MOD_STRIP=1/g' gce-install.sh
+$ sed -i 's/cp config.gce .config/cp config-4.18.0-477.21.1.el8_8.x86_64 .config\nscripts\/kconfig\/merge_config.sh -m config.gce config-4.18.0-477.21.1.el8_8.x86_64/g' gce-install.sh
+```
+
+Modify the `config-4.18.0-477.21.1.el8_8.x86_64` file to set up some options for the kernel installation
+```
+$ sed -i 's/CONFIG_SYSTEM_TRUSTED_KEYS="certs\/rhel.pem"/CONFIG_SYSTEM_TRUSTED_KEYS=""/g' config-4.18.0-477.21.1.el8_8.x86_64
+$ sed -i 's/CONFIG_SYSTEM_REVOCATION_KEYS="debian\/canonical-revoked-certs.pem"/CONFIG_SYSTEM_REVOCATION_KEYS=""/g' config-4.18.0-477.21.1.el8_8.x86_64
+$ sed -i 's/CONFIG_DEBUG_INFO_BTF=y/CONFIG_DEBUG_INFO_BTF=n/g' config-4.18.0-477.21.1.el8_8.x86_64
+$ sed -i 's/CONFIG_DEBUG_INFO_BTF_MODULES=y/CONFIG_DEBUG_INFO_BTF_MODULES=n/g' config-4.18.0-477.21.1.el8_8.x86_64
+```
+
+Build the kernel
+```
+$ ./gce-install.sh -m localhost
+# Wait until the end. The VM will automatically reboot. It takes some time...
+```
+
+Compile the kernel
+```
+$ tar --no-same-owner -xzvf kernel-+v3+6e321d1c986a+GCE.tar.gz2 -C /
+$ depmod -a 6.4.0+v3+6e321d1c986a+GCE
+$ dracut -f -v --hostonly -k '/lib/modules/6.4.0+v3+6e321d1c986a+GCE' /boot/initramfs-6.4.0+v3+6e321d1c986a+GCE.img 6.4.0+v3+6e321d1c986a+GCE
+```
+
+Set the kernel as the default one and reboot the machine
+```
+$ grubby --grub2 --add-kernel=/boot/vmlinuz-6.4.0+v3+6e321d1c986a+GCE --title="Linux BBRv3" --initrd=/boot/initramfs-6.4.0+v3+6e321d1c986a+GCE.img --copy-default
+$ grubby --set-default /boot/vmlinuz-6.4.0+v3+6e321d1c986a+GCE
+$ grubby --default-kernel
+$ grubby --info=ALL
+$ reboot
+```
+
+Verify the successful kernel installation
+```
+$ uname -a
+# You should see the branch name SHA1 hash, and build time stamp from the kernel you built above.
+# Linux bbrv3-vm.cern.ch 6.4.0+v3+6e321d1c986a+GCE #1 SMP PREEMPT_DYNAMIC Tue Oct  3 17:18:46 CEST 2023 x86_64 x86_64 x86_64 GNU/Linux
+```
+
+Enable BBRv3 in the kernel
+```
+$ modprobe tcp_dctcp
+$ modprobe tcp_bbr
+$ bash -c "echo 'tcp_dctcp' > /etc/modules-load.d/dctcp.conf"
+$ bash -c "echo 'tcp_bbr' > /etc/modules-load.d/bbr.conf"
+```
+
+Verify that BBRv3 is enable in the kernel
+```
+$ sysctl net.ipv4.tcp_available_congestion_control
+# Output: net.ipv4.tcp_available_congestion_control = reno bbr1 cubic dctcp bbr
+```
+
+Run `iperf3` with BBR pace at 6 Gb/s in both directions
+```
+$ iperf3 -C bbr --fq-rate 6G -c remote_host
+```