Add NAT networking with bridge, veth, DNS, routing, and firewall configuration for containers.

Signed-off-by: Richard Qin <richard.qin.x@gmail.com>

4 files changed, 107 insertions, 3 deletions

diff --git a/debian-container/README b/debian-container/README
index c0ef344..0328def 100644
--- a/debian-container/README
+++ b/debian-container/README
@@ -46,6 +46,7 @@ sudo ./debian-container.sh resize test-3 --size 12G
 
 sudo ./debian-container.sh enter test-1
 sudo ./debian-container.sh enter test-1 --network host
+sudo ./debian-container.sh enter test-1 --network nat
 sudo ./debian-container.sh enter test-1 --mount /home/richard/project:/workspace:rw
 sudo ./debian-container.sh enter test-1 --mount /home/richard/data:/data:ro
 
@@ -53,6 +54,7 @@ sudo ./debian-container.sh enter test-1 --mount /home/richard/data:/data:ro
 
 sudo ./debian-container.sh exec test-1 -- uname -a
 sudo ./debian-container.sh exec test-1 --network host -- apt-get update
+sudo ./debian-container.sh exec test-1 --network nat -- apt-get update
 sudo ./debian-container.sh exec test-1 --mount /home/richard/project:/workspace:rw -- make -C /workspace
 
 列出和查看容器：
@@ -95,7 +97,12 @@ DEBIAN_ARCH     目标架构
 DEBIAN_MIRROR   Debian 镜像地址
 DEBIAN_INCLUDE  额外软件包，使用逗号分隔
 DEBIAN_EXCLUDE  要排除的软件包，使用逗号分隔
-DEBIAN_NETWORK  默认网络模式，none 或 host
+DEBIAN_NETWORK  默认网络模式，none、host 或 nat
+DEBIAN_NAT_BRIDGE  NAT 网桥名称，默认 rutils0
+DEBIAN_NAT_NETWORK NAT 子网，默认 10.88.0.0/24
+DEBIAN_NAT_GATEWAY NAT 网关地址，默认 10.88.0.1
+DEBIAN_NAT_ADDRESS NAT 容器地址，默认 10.88.0.2
+DEBIAN_NAT_DNS NAT 模式 DNS，默认 1.1.1.1
 
 挂载参数格式：
 
diff --git a/debian-container/lib/common.sh b/debian-container/lib/common.sh
index 6177482..075cd15 100644
--- a/debian-container/lib/common.sh
+++ b/debian-container/lib/common.sh
@@ -77,7 +77,7 @@ base-create 选项：
   --exclude PACKAGES  要排除的软件包，使用逗号分隔
 
 网络选项：
-  --network MODE      网络模式：none（默认）或 host
+  --network MODE      网络模式：none（默认）、host 或 nat
 
 挂载选项：
   --mount SPEC        目录挂载：HOST:CONTAINER[:ro|rw]
@@ -97,6 +97,11 @@ profile 配置项：
   DEBIAN_INCLUDE    额外软件包，使用逗号分隔
   DEBIAN_EXCLUDE    要排除的软件包，使用逗号分隔
   DEBIAN_NETWORK    默认网络模式（默认：none）
+  DEBIAN_NAT_BRIDGE NAT 网桥名称（默认：rutils0）
+  DEBIAN_NAT_NETWORK NAT 子网（默认：10.88.0.0/24）
+  DEBIAN_NAT_GATEWAY NAT 网关地址（默认：10.88.0.1）
+  DEBIAN_NAT_ADDRESS 容器地址（默认：10.88.0.2）
+  DEBIAN_NAT_DNS    NAT 模式 DNS（默认：1.1.1.1）
 EOF
 }
 
diff --git a/debian-container/lib/container.sh b/debian-container/lib/container.sh
index b3d8c9b..62ab0b3 100644
--- a/debian-container/lib/container.sh
+++ b/debian-container/lib/container.sh
@@ -247,6 +247,11 @@ dc_enter() {
     bind_args+=(--mount "$spec")
   done
 
+  if [[ "$network_mode" == nat ]]; then
+    dc_network_nat_run _enter "${bind_args[@]}"
+    return
+  fi
+
   unshare --mount --uts --ipc --pid --fork --propagation private \
     "${DC_NETWORK_UNSHARE_ARGS[@]}" -- bash "$DC_SCRIPT" _enter "$DC_INSTANCE" "${bind_args[@]}"
 }
@@ -255,6 +260,7 @@ dc_enter_rootfs() {
   dc_bind_load_options "$@"
   dc_mount_root
   trap dc_cleanup_mounts EXIT
+  dc_network_configure_rootfs
   dc_mount_virtual_filesystems
   dc_bind_mount_all
   hostname debian-container
@@ -306,6 +312,11 @@ dc_exec() {
     bind_args+=(--mount "$spec")
   done
 
+  if [[ "$network_mode" == nat ]]; then
+    dc_network_nat_run _exec "${bind_args[@]}" -- "$@"
+    return
+  fi
+
   unshare --mount --uts --ipc --pid --fork --propagation private \
     "${DC_NETWORK_UNSHARE_ARGS[@]}" -- \
     bash "$DC_SCRIPT" _exec "$DC_INSTANCE" "${bind_args[@]}" -- "$@"
@@ -335,6 +346,7 @@ dc_exec_rootfs() {
   (($# > 0)) || dc_die 'exec 需要一个命令。'
   dc_mount_root
   trap dc_cleanup_mounts EXIT
+  dc_network_configure_rootfs
   dc_mount_virtual_filesystems
   dc_bind_mount_all
   hostname debian-container
diff --git a/debian-container/lib/network.sh b/debian-container/lib/network.sh
index 333869f..a5a31dd 100644
--- a/debian-container/lib/network.sh
+++ b/debian-container/lib/network.sh
@@ -4,6 +4,12 @@
 
 DC_NETWORK_MODE=${DEBIAN_NETWORK:-none}
 DC_NETWORK_UNSHARE_ARGS=()
+DC_NAT_BRIDGE=${DEBIAN_NAT_BRIDGE:-rutils0}
+DC_NAT_NETWORK=${DEBIAN_NAT_NETWORK:-10.88.0.0/24}
+DC_NAT_PREFIX=${DC_NAT_NETWORK#*/}
+DC_NAT_GATEWAY=${DEBIAN_NAT_GATEWAY:-10.88.0.1}
+DC_NAT_ADDRESS=${DEBIAN_NAT_ADDRESS:-10.88.0.2}
+DC_NAT_DNS=${DEBIAN_NAT_DNS:-1.1.1.1}
 
 dc_network_prepare() {
   local mode=${1:-$DC_NETWORK_MODE}
@@ -15,8 +21,82 @@ dc_network_prepare() {
     host)
       DC_NETWORK_UNSHARE_ARGS=()
       ;;
+    nat)
+      DC_NETWORK_UNSHARE_ARGS=(--net)
+      ;;
     *)
-      dc_die "网络模式无效：$mode（可选：none、host）"
+      dc_die "网络模式无效：$mode（可选：none、host、nat）"
       ;;
   esac
 }
+
+dc_network_configure_rootfs() {
+  [[ "$DC_NETWORK_MODE" == nat ]] || return 0
+  rm -f "$DC_ROOT/etc/resolv.conf"
+  printf 'nameserver %s\n' "$DC_NAT_DNS" > "$DC_ROOT/etc/resolv.conf"
+}
+
+dc_network_nat_setup_firewall() {
+  dc_require_commands grep nft sysctl
+
+  sysctl -w net.ipv4.ip_forward=1 >/dev/null
+  if ! nft list table ip rutils_nat >/dev/null 2>&1; then
+    nft add table ip rutils_nat
+  fi
+  if ! nft list chain ip rutils_nat postrouting >/dev/null 2>&1; then
+    nft 'add chain ip rutils_nat postrouting { type nat hook postrouting priority 100; policy accept; }'
+  fi
+  if ! nft list chain ip rutils_nat postrouting | grep -Fq "ip saddr $DC_NAT_NETWORK"; then
+    nft add rule ip rutils_nat postrouting ip saddr "$DC_NAT_NETWORK" oifname != "$DC_NAT_BRIDGE" masquerade
+  fi
+}
+
+dc_network_nat_setup() {
+  local netns=$1
+  local host_interface=$2
+  local guest_interface=$3
+
+  dc_require_commands grep ip
+  if ! ip link show "$DC_NAT_BRIDGE" >/dev/null 2>&1; then
+    ip link add "$DC_NAT_BRIDGE" type bridge
+  fi
+  ip link set "$DC_NAT_BRIDGE" up
+  if ! ip -4 addr show dev "$DC_NAT_BRIDGE" | grep -Fq "inet $DC_NAT_GATEWAY/"; then
+    ip addr add "$DC_NAT_GATEWAY/$DC_NAT_PREFIX" dev "$DC_NAT_BRIDGE"
+  fi
+
+  ip netns add "$netns"
+  ip link add "$host_interface" type veth peer name "$guest_interface"
+  ip link set "$guest_interface" netns "$netns"
+  ip link set "$host_interface" master "$DC_NAT_BRIDGE"
+  ip link set "$host_interface" up
+
+  ip netns exec "$netns" ip link set lo up
+  ip netns exec "$netns" ip link set "$guest_interface" name eth0
+  ip netns exec "$netns" ip addr add "$DC_NAT_ADDRESS/$DC_NAT_PREFIX" dev eth0
+  ip netns exec "$netns" ip link set eth0 up
+  ip netns exec "$netns" ip route add default via "$DC_NAT_GATEWAY"
+  dc_network_nat_setup_firewall
+}
+
+dc_network_nat_cleanup() {
+  local netns=$1
+  local host_interface=$2
+
+  ip link delete "$host_interface" 2>/dev/null || true
+  ip netns delete "$netns" 2>/dev/null || true
+}
+
+dc_network_nat_run() {
+  local child_action=$1
+  local netns="rutils-${DC_INSTANCE}-$$"
+  local host_interface="rvh$$"
+  local guest_interface="rvg$$"
+
+  shift
+  trap "dc_network_nat_cleanup '$netns' '$host_interface'" EXIT
+  dc_network_nat_setup "$netns" "$host_interface" "$guest_interface"
+  env DEBIAN_NETWORK=nat ip netns exec "$netns" \
+    unshare --mount --uts --ipc --pid --fork --propagation private -- \
+    bash "$DC_SCRIPT" "$child_action" "$DC_INSTANCE" "$@"
+}