bpf: add bpf_xdp_adjust_tail sample prog
adding bpf's sample program which is using bpf_xdp_adjust_tail helper by generating ICMPv4 "packet to big" message if ingress packet's size is bigger then 600 bytes Signed-off-by: Nikita V. Shirokov <tehnerd@tehnerd.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
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0367d0a294
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@ -44,6 +44,7 @@ hostprogs-y += xdp_monitor
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hostprogs-y += xdp_rxq_info
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hostprogs-y += syscall_tp
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hostprogs-y += cpustat
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hostprogs-y += xdp_adjust_tail
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# Libbpf dependencies
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LIBBPF := ../../tools/lib/bpf/bpf.o ../../tools/lib/bpf/nlattr.o
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@ -95,6 +96,7 @@ xdp_monitor-objs := bpf_load.o $(LIBBPF) xdp_monitor_user.o
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xdp_rxq_info-objs := bpf_load.o $(LIBBPF) xdp_rxq_info_user.o
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syscall_tp-objs := bpf_load.o $(LIBBPF) syscall_tp_user.o
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cpustat-objs := bpf_load.o $(LIBBPF) cpustat_user.o
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xdp_adjust_tail-objs := bpf_load.o $(LIBBPF) xdp_adjust_tail_user.o
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# Tell kbuild to always build the programs
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always := $(hostprogs-y)
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@ -148,6 +150,7 @@ always += xdp_rxq_info_kern.o
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always += xdp2skb_meta_kern.o
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always += syscall_tp_kern.o
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always += cpustat_kern.o
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always += xdp_adjust_tail_kern.o
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HOSTCFLAGS += -I$(objtree)/usr/include
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HOSTCFLAGS += -I$(srctree)/tools/lib/
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@ -193,6 +196,7 @@ HOSTLOADLIBES_xdp_monitor += -lelf
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HOSTLOADLIBES_xdp_rxq_info += -lelf
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HOSTLOADLIBES_syscall_tp += -lelf
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HOSTLOADLIBES_cpustat += -lelf
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HOSTLOADLIBES_xdp_adjust_tail += -lelf
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# Allows pointing LLC/CLANG to a LLVM backend with bpf support, redefine on cmdline:
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# make samples/bpf/ LLC=~/git/llvm/build/bin/llc CLANG=~/git/llvm/build/bin/clang
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152
samples/bpf/xdp_adjust_tail_kern.c
Normal file
152
samples/bpf/xdp_adjust_tail_kern.c
Normal file
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@ -0,0 +1,152 @@
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/* SPDX-License-Identifier: GPL-2.0
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* Copyright (c) 2018 Facebook
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of version 2 of the GNU General Public
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* License as published by the Free Software Foundation.
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*
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* This program shows how to use bpf_xdp_adjust_tail() by
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* generating ICMPv4 "packet to big" (unreachable/ df bit set frag needed
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* to be more preice in case of v4)" where receiving packets bigger then
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* 600 bytes.
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*/
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#define KBUILD_MODNAME "foo"
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#include <uapi/linux/bpf.h>
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#include <linux/in.h>
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#include <linux/if_ether.h>
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#include <linux/if_packet.h>
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#include <linux/if_vlan.h>
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#include <linux/ip.h>
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#include <linux/icmp.h>
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#include "bpf_helpers.h"
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#define DEFAULT_TTL 64
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#define MAX_PCKT_SIZE 600
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#define ICMP_TOOBIG_SIZE 98
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#define ICMP_TOOBIG_PAYLOAD_SIZE 92
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struct bpf_map_def SEC("maps") icmpcnt = {
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.type = BPF_MAP_TYPE_ARRAY,
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.key_size = sizeof(__u32),
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.value_size = sizeof(__u64),
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.max_entries = 1,
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};
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static __always_inline void count_icmp(void)
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{
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u64 key = 0;
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u64 *icmp_count;
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icmp_count = bpf_map_lookup_elem(&icmpcnt, &key);
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if (icmp_count)
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*icmp_count += 1;
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}
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static __always_inline void swap_mac(void *data, struct ethhdr *orig_eth)
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{
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struct ethhdr *eth;
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eth = data;
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memcpy(eth->h_source, orig_eth->h_dest, ETH_ALEN);
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memcpy(eth->h_dest, orig_eth->h_source, ETH_ALEN);
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eth->h_proto = orig_eth->h_proto;
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}
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static __always_inline __u16 csum_fold_helper(__u32 csum)
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{
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return ~((csum & 0xffff) + (csum >> 16));
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}
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static __always_inline void ipv4_csum(void *data_start, int data_size,
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__u32 *csum)
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{
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*csum = bpf_csum_diff(0, 0, data_start, data_size, *csum);
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*csum = csum_fold_helper(*csum);
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}
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static __always_inline int send_icmp4_too_big(struct xdp_md *xdp)
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{
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int headroom = (int)sizeof(struct iphdr) + (int)sizeof(struct icmphdr);
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if (bpf_xdp_adjust_head(xdp, 0 - headroom))
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return XDP_DROP;
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void *data = (void *)(long)xdp->data;
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void *data_end = (void *)(long)xdp->data_end;
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if (data + (ICMP_TOOBIG_SIZE + headroom) > data_end)
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return XDP_DROP;
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struct iphdr *iph, *orig_iph;
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struct icmphdr *icmp_hdr;
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struct ethhdr *orig_eth;
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__u32 csum = 0;
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__u64 off = 0;
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orig_eth = data + headroom;
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swap_mac(data, orig_eth);
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off += sizeof(struct ethhdr);
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iph = data + off;
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off += sizeof(struct iphdr);
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icmp_hdr = data + off;
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off += sizeof(struct icmphdr);
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orig_iph = data + off;
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icmp_hdr->type = ICMP_DEST_UNREACH;
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icmp_hdr->code = ICMP_FRAG_NEEDED;
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icmp_hdr->un.frag.mtu = htons(MAX_PCKT_SIZE-sizeof(struct ethhdr));
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icmp_hdr->checksum = 0;
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ipv4_csum(icmp_hdr, ICMP_TOOBIG_PAYLOAD_SIZE, &csum);
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icmp_hdr->checksum = csum;
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iph->ttl = DEFAULT_TTL;
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iph->daddr = orig_iph->saddr;
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iph->saddr = orig_iph->daddr;
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iph->version = 4;
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iph->ihl = 5;
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iph->protocol = IPPROTO_ICMP;
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iph->tos = 0;
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iph->tot_len = htons(
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ICMP_TOOBIG_SIZE + headroom - sizeof(struct ethhdr));
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iph->check = 0;
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csum = 0;
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ipv4_csum(iph, sizeof(struct iphdr), &csum);
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iph->check = csum;
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count_icmp();
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return XDP_TX;
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}
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static __always_inline int handle_ipv4(struct xdp_md *xdp)
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{
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void *data_end = (void *)(long)xdp->data_end;
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void *data = (void *)(long)xdp->data;
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int pckt_size = data_end - data;
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int offset;
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if (pckt_size > MAX_PCKT_SIZE) {
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offset = pckt_size - ICMP_TOOBIG_SIZE;
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if (bpf_xdp_adjust_tail(xdp, 0 - offset))
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return XDP_PASS;
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return send_icmp4_too_big(xdp);
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}
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return XDP_PASS;
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}
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SEC("xdp_icmp")
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int _xdp_icmp(struct xdp_md *xdp)
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{
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void *data_end = (void *)(long)xdp->data_end;
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void *data = (void *)(long)xdp->data;
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struct ethhdr *eth = data;
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__u16 h_proto;
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if (eth + 1 > data_end)
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return XDP_DROP;
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h_proto = eth->h_proto;
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if (h_proto == htons(ETH_P_IP))
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return handle_ipv4(xdp);
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else
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return XDP_PASS;
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}
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char _license[] SEC("license") = "GPL";
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142
samples/bpf/xdp_adjust_tail_user.c
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142
samples/bpf/xdp_adjust_tail_user.c
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@ -0,0 +1,142 @@
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/* SPDX-License-Identifier: GPL-2.0
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* Copyright (c) 2018 Facebook
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of version 2 of the GNU General Public
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* License as published by the Free Software Foundation.
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*/
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#include <linux/bpf.h>
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#include <linux/if_link.h>
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#include <assert.h>
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#include <errno.h>
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#include <signal.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/resource.h>
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#include <arpa/inet.h>
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#include <netinet/ether.h>
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#include <unistd.h>
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#include <time.h>
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#include "bpf_load.h"
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#include "libbpf.h"
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#include "bpf_util.h"
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#define STATS_INTERVAL_S 2U
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static int ifindex = -1;
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static __u32 xdp_flags;
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static void int_exit(int sig)
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{
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if (ifindex > -1)
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bpf_set_link_xdp_fd(ifindex, -1, xdp_flags);
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exit(0);
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}
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/* simple "icmp packet too big sent" counter
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*/
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static void poll_stats(unsigned int kill_after_s)
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{
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time_t started_at = time(NULL);
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__u64 value = 0;
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int key = 0;
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while (!kill_after_s || time(NULL) - started_at <= kill_after_s) {
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sleep(STATS_INTERVAL_S);
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assert(bpf_map_lookup_elem(map_fd[0], &key, &value) == 0);
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printf("icmp \"packet too big\" sent: %10llu pkts\n", value);
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}
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}
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static void usage(const char *cmd)
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{
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printf("Start a XDP prog which send ICMP \"packet too big\" \n"
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"messages if ingress packet is bigger then MAX_SIZE bytes\n");
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printf("Usage: %s [...]\n", cmd);
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printf(" -i <ifindex> Interface Index\n");
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printf(" -T <stop-after-X-seconds> Default: 0 (forever)\n");
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printf(" -S use skb-mode\n");
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printf(" -N enforce native mode\n");
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printf(" -h Display this help\n");
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}
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int main(int argc, char **argv)
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{
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unsigned char opt_flags[256] = {};
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unsigned int kill_after_s = 0;
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const char *optstr = "i:T:SNh";
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struct rlimit r = {RLIM_INFINITY, RLIM_INFINITY};
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char filename[256];
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int opt;
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int i;
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for (i = 0; i < strlen(optstr); i++)
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if (optstr[i] != 'h' && 'a' <= optstr[i] && optstr[i] <= 'z')
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opt_flags[(unsigned char)optstr[i]] = 1;
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while ((opt = getopt(argc, argv, optstr)) != -1) {
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switch (opt) {
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case 'i':
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ifindex = atoi(optarg);
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break;
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case 'T':
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kill_after_s = atoi(optarg);
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break;
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case 'S':
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xdp_flags |= XDP_FLAGS_SKB_MODE;
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break;
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case 'N':
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xdp_flags |= XDP_FLAGS_DRV_MODE;
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break;
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default:
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usage(argv[0]);
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return 1;
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}
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opt_flags[opt] = 0;
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}
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for (i = 0; i < strlen(optstr); i++) {
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if (opt_flags[(unsigned int)optstr[i]]) {
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fprintf(stderr, "Missing argument -%c\n", optstr[i]);
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usage(argv[0]);
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return 1;
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}
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}
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if (setrlimit(RLIMIT_MEMLOCK, &r)) {
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perror("setrlimit(RLIMIT_MEMLOCK, RLIM_INFINITY)");
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return 1;
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}
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snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
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if (load_bpf_file(filename)) {
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printf("%s", bpf_log_buf);
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return 1;
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}
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if (!prog_fd[0]) {
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printf("load_bpf_file: %s\n", strerror(errno));
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return 1;
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}
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signal(SIGINT, int_exit);
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signal(SIGTERM, int_exit);
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if (bpf_set_link_xdp_fd(ifindex, prog_fd[0], xdp_flags) < 0) {
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printf("link set xdp fd failed\n");
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return 1;
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}
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poll_stats(kill_after_s);
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bpf_set_link_xdp_fd(ifindex, -1, xdp_flags);
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return 0;
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}
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@ -132,6 +132,8 @@ static int (*bpf_l3_csum_replace)(void *ctx, int off, int from, int to, int flag
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(void *) BPF_FUNC_l3_csum_replace;
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static int (*bpf_l4_csum_replace)(void *ctx, int off, int from, int to, int flags) =
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(void *) BPF_FUNC_l4_csum_replace;
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static int (*bpf_csum_diff)(void *from, int from_size, void *to, int to_size, int seed) =
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(void *) BPF_FUNC_csum_diff;
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static int (*bpf_skb_under_cgroup)(void *ctx, void *map, int index) =
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(void *) BPF_FUNC_skb_under_cgroup;
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static int (*bpf_skb_change_head)(void *, int len, int flags) =
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