add basic l3dsr dscp

examples/basic_l3dsr/dscp/Dockerfile

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+
+FROM ubuntu:22.04
+
+RUN apt update \
+ && apt install -y libc6-dev-i386 clang libbpf-dev iproute2

examples/basic_l3dsr/dscp/spec.yaml

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+preinit:
+  - cmds:
+    - cmd: docker build -t xdptmp .
+
+nodes:
+  - name: R1
+    image: xdptmp
+    interfaces:
+      - { name: net1, type: direct, args: CLOS#net1 }
+    sysctls:
+      - sysctl: net.ipv4.ip_forward=1
+      - sysctl: net.ipv4.conf.all.rp_filter=0
+      - sysctl: net.ipv4.conf.default.rp_filter=0
+
+  - name: C1
+    image: slankdev/mikanectl
+    docker_run_extra_args: --entrypoint bash
+    interfaces:
+      - { name: net0, type: direct, args: CLOS#net0 }
+    sysctls:
+      - sysctl: net.ipv4.ip_forward=1
+      - sysctl: net.ipv4.conf.all.rp_filter=0
+      - sysctl: net.ipv4.conf.default.rp_filter=0
+
+  - name: C2
+    image: slankdev/mikanectl
+    docker_run_extra_args: --entrypoint bash
+    interfaces:
+      - { name: net2, type: direct, args: CLOS#net2 }
+    sysctls:
+      - sysctl: net.ipv4.ip_forward=1
+      - sysctl: net.ipv4.conf.all.rp_filter=0
+      - sysctl: net.ipv4.conf.default.rp_filter=0
+
+  - name: CLOS
+    image: nicolaka/netshoot
+    interfaces:
+      - { name: net0, type: direct, args: C1#net0 }
+      - { name: net1, type: direct, args: R1#net1 }
+      - { name: net2, type: direct, args: C2#net2 }
+    sysctls:
+      - sysctl: net.ipv4.ip_forward=1
+      - sysctl: net.ipv4.conf.all.rp_filter=0
+      - sysctl: net.ipv4.conf.default.rp_filter=0
+
+postinit:
+  cmds:
+  - cmd: docker cp xdp.c R1:/root/xdp.c
+  - cmd: docker exec R1 clang -O2 -Wall -target bpf -c /root/xdp.c
+  - cmd: docker exec R1 ip link set net1 xdpgeneric obj lb.o sec xdp-lb
+
+node_configs:
+  - name: R1
+    cmds:
+      - cmd: ip addr add 142.0.0.1/32 dev lo
+      - cmd: ip addr add 10.0.1.1/24 dev net1
+      - cmd: ip route add default via 10.0.1.2
+  - name: C1
+    cmds:
+      - cmd: ip addr add 10.0.0.1/24 dev net0
+      - cmd: ip route add default via 10.0.0.2
+  - name: C2
+    cmds:
+      - cmd: nohup mikanectl ifconfig-http -p 80 &
+      - cmd: ip addr add 10.0.2.1/24 dev net2
+      - cmd: ip route add default via 10.0.2.2
+      - cmd: ip route add local 142.0.0.1/32 dev lo
+      - cmd: tc qdisc add dev net2 clsact
+      - cmd: tc filter add dev net2 ingress u32 match ip dsfield 0xa 0x1e action nat ingress 10.0.2.1 142.0.0.1
+
+  - name: CLOS
+    cmds:
+      - cmd: ip addr add 10.0.0.2/24 dev net0
+      - cmd: ip addr add 10.0.1.2/24 dev net1
+      - cmd: ip addr add 10.0.2.2/24 dev net2
+      - cmd: ip route add 142.0.0.1/32 dev net1

examples/basic_l3dsr/dscp/xdp.c

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+#include <linux/bpf.h>
+#include <linux/if_ether.h>
+#include <linux/icmp.h>
+#include <linux/ip.h>
+#include <linux/in.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_endian.h>
+
+#ifndef DSCP
+#define DSCP 10
+#endif
+
+static __always_inline __u16 csum_fold_helper(__u64 csum) {
+  int i;
+#pragma unroll
+  for (i = 0; i < 4; i ++) {
+    if (csum >> 16)
+      csum = (csum & 0xffff) + (csum >> 16);
+  }
+  return ~csum;
+}
+
+static __always_inline void ipv4_csum(void *data_start, int data_size,  __u64 *csum) {
+  *csum = bpf_csum_diff(0, 0, data_start, data_size, *csum);
+  *csum = csum_fold_helper(*csum);
+}
+
+static __always_inline int process_ipv4(struct xdp_md* ctx,
+  __u64 data, __u64 data_end) {
+  __u8 src_mac[ETH_ALEN];
+  struct ethhdr *eth;
+  struct iphdr *iph;
+
+  __u32 dst_addr = 0xa000201;
+  __u64 csum = 0;
+
+  eth = (struct ethhdr*)(data);
+
+  if ((__u64)(eth + 1) > data_end)
+    return XDP_DROP;
+
+  iph = (struct iphdr*)(data + sizeof(struct ethhdr));
+
+  if ((__u64)(iph + 1) > data_end)
+    return XDP_DROP;
+
+  if (iph->daddr == bpf_htonl(0x8e000001)) {
+    iph->tos = DSCP;
+    iph->daddr = bpf_htonl(dst_addr);
+    iph->check = 0;
+    ipv4_csum(iph, sizeof(struct iphdr), &csum);
+    iph->check = csum;
+
+    __builtin_memcpy(src_mac, eth->h_source, ETH_ALEN);
+    __builtin_memcpy(eth->h_source, eth->h_dest, ETH_ALEN);
+    __builtin_memcpy(eth->h_dest, src_mac, ETH_ALEN);
+
+    return XDP_TX;
+  }
+  return XDP_PASS;
+}
+
+static __always_inline int process_eth(struct xdp_md* ctx) {
+  __u64 data = ctx->data;
+  __u64 data_end = ctx->data_end;
+  struct ethhdr *eth;
+
+  eth = (struct ethhdr*)data;
+
+  if ((__u64)(eth + 1) > data_end)
+    return XDP_DROP;
+
+  if (eth->h_proto == bpf_htons(ETH_P_IP)) {
+    return process_ipv4(ctx, data, data_end);
+  }
+  return XDP_PASS;
+}
+
+SEC("xdp-lb")
+int entry(struct xdp_md *ctx) {
+  int ret = process_eth(ctx);
+  return ret;
+}
+
+char __license[] SEC("license") = "GPL";