bpf: add bpf_xdp_adjust_tail sample prog (c6ffd1ff) · Commits · 戴 / test

samples/bpf/Makefile

+4 −0

Original line number	Diff line number	Diff line
		@@ -44,6 +44,7 @@ hostprogs-y += xdp_monitor
		hostprogs-y += xdp_rxq_info
		hostprogs-y += syscall_tp
		hostprogs-y += cpustat
		hostprogs-y += xdp_adjust_tail

		# Libbpf dependencies
		LIBBPF := ../../tools/lib/bpf/bpf.o ../../tools/lib/bpf/nlattr.o
		@@ -95,6 +96,7 @@ xdp_monitor-objs := bpf_load.o $(LIBBPF) xdp_monitor_user.o
		xdp_rxq_info-objs := bpf_load.o $(LIBBPF) xdp_rxq_info_user.o
		syscall_tp-objs := bpf_load.o $(LIBBPF) syscall_tp_user.o
		cpustat-objs := bpf_load.o $(LIBBPF) cpustat_user.o
		xdp_adjust_tail-objs := bpf_load.o $(LIBBPF) xdp_adjust_tail_user.o

		# Tell kbuild to always build the programs
		always := $(hostprogs-y)
		@@ -148,6 +150,7 @@ always += xdp_rxq_info_kern.o
		always += xdp2skb_meta_kern.o
		always += syscall_tp_kern.o
		always += cpustat_kern.o
		always += xdp_adjust_tail_kern.o

		HOSTCFLAGS += -I$(objtree)/usr/include
		HOSTCFLAGS += -I$(srctree)/tools/lib/
		@@ -193,6 +196,7 @@ HOSTLOADLIBES_xdp_monitor += -lelf
		HOSTLOADLIBES_xdp_rxq_info += -lelf
		HOSTLOADLIBES_syscall_tp += -lelf
		HOSTLOADLIBES_cpustat += -lelf
		HOSTLOADLIBES_xdp_adjust_tail += -lelf

		# Allows pointing LLC/CLANG to a LLVM backend with bpf support, redefine on cmdline:
		# make samples/bpf/ LLC=~/git/llvm/build/bin/llc CLANG=~/git/llvm/build/bin/clang

samples/bpf/xdp_adjust_tail_kern.c

0 → 100644

+152 −0

Original line number	Diff line number	Diff line
		/* SPDX-License-Identifier: GPL-2.0
		* Copyright (c) 2018 Facebook
		*
		* This program is free software; you can redistribute it and/or
		* modify it under the terms of version 2 of the GNU General Public
		* License as published by the Free Software Foundation.
		*
		* This program shows how to use bpf_xdp_adjust_tail() by
		* generating ICMPv4 "packet to big" (unreachable/ df bit set frag needed
		* to be more preice in case of v4)" where receiving packets bigger then
		* 600 bytes.
		*/
		#define KBUILD_MODNAME "foo"
		#include <uapi/linux/bpf.h>
		#include <linux/in.h>
		#include <linux/if_ether.h>
		#include <linux/if_packet.h>
		#include <linux/if_vlan.h>
		#include <linux/ip.h>
		#include <linux/icmp.h>
		#include "bpf_helpers.h"

		#define DEFAULT_TTL 64
		#define MAX_PCKT_SIZE 600
		#define ICMP_TOOBIG_SIZE 98
		#define ICMP_TOOBIG_PAYLOAD_SIZE 92

		struct bpf_map_def SEC("maps") icmpcnt = {
		.type = BPF_MAP_TYPE_ARRAY,
		.key_size = sizeof(__u32),
		.value_size = sizeof(__u64),
		.max_entries = 1,
		};

		static __always_inline void count_icmp(void)
		{
		u64 key = 0;
		u64 *icmp_count;

		icmp_count = bpf_map_lookup_elem(&icmpcnt, &key);
		if (icmp_count)
		*icmp_count += 1;
		}

		static __always_inline void swap_mac(void data, struct ethhdr orig_eth)
		{
		struct ethhdr *eth;

		eth = data;
		memcpy(eth->h_source, orig_eth->h_dest, ETH_ALEN);
		memcpy(eth->h_dest, orig_eth->h_source, ETH_ALEN);
		eth->h_proto = orig_eth->h_proto;
		}

		static __always_inline __u16 csum_fold_helper(__u32 csum)
		{
		return ~((csum & 0xffff) + (csum >> 16));
		}

		static __always_inline void ipv4_csum(void *data_start, int data_size,
		__u32 *csum)
		{
		csum = bpf_csum_diff(0, 0, data_start, data_size, csum);
		csum = csum_fold_helper(csum);
		}

		static __always_inline int send_icmp4_too_big(struct xdp_md *xdp)
		{
		int headroom = (int)sizeof(struct iphdr) + (int)sizeof(struct icmphdr);

		if (bpf_xdp_adjust_head(xdp, 0 - headroom))
		return XDP_DROP;
		void data = (void )(long)xdp->data;
		void data_end = (void )(long)xdp->data_end;

		if (data + (ICMP_TOOBIG_SIZE + headroom) > data_end)
		return XDP_DROP;

		struct iphdr iph, orig_iph;
		struct icmphdr *icmp_hdr;
		struct ethhdr *orig_eth;
		__u32 csum = 0;
		__u64 off = 0;

		orig_eth = data + headroom;
		swap_mac(data, orig_eth);
		off += sizeof(struct ethhdr);
		iph = data + off;
		off += sizeof(struct iphdr);
		icmp_hdr = data + off;
		off += sizeof(struct icmphdr);
		orig_iph = data + off;
		icmp_hdr->type = ICMP_DEST_UNREACH;
		icmp_hdr->code = ICMP_FRAG_NEEDED;
		icmp_hdr->un.frag.mtu = htons(MAX_PCKT_SIZE-sizeof(struct ethhdr));
		icmp_hdr->checksum = 0;
		ipv4_csum(icmp_hdr, ICMP_TOOBIG_PAYLOAD_SIZE, &csum);
		icmp_hdr->checksum = csum;
		iph->ttl = DEFAULT_TTL;
		iph->daddr = orig_iph->saddr;
		iph->saddr = orig_iph->daddr;
		iph->version = 4;
		iph->ihl = 5;
		iph->protocol = IPPROTO_ICMP;
		iph->tos = 0;
		iph->tot_len = htons(
		ICMP_TOOBIG_SIZE + headroom - sizeof(struct ethhdr));
		iph->check = 0;
		csum = 0;
		ipv4_csum(iph, sizeof(struct iphdr), &csum);
		iph->check = csum;
		count_icmp();
		return XDP_TX;
		}


		static __always_inline int handle_ipv4(struct xdp_md *xdp)
		{
		void data_end = (void )(long)xdp->data_end;
		void data = (void )(long)xdp->data;
		int pckt_size = data_end - data;
		int offset;

		if (pckt_size > MAX_PCKT_SIZE) {
		offset = pckt_size - ICMP_TOOBIG_SIZE;
		if (bpf_xdp_adjust_tail(xdp, 0 - offset))
		return XDP_PASS;
		return send_icmp4_too_big(xdp);
		}
		return XDP_PASS;
		}

		SEC("xdp_icmp")
		int _xdp_icmp(struct xdp_md *xdp)
		{
		void data_end = (void )(long)xdp->data_end;
		void data = (void )(long)xdp->data;
		struct ethhdr *eth = data;
		__u16 h_proto;

		if (eth + 1 > data_end)
		return XDP_DROP;

		h_proto = eth->h_proto;

		if (h_proto == htons(ETH_P_IP))
		return handle_ipv4(xdp);
		else
		return XDP_PASS;
		}

		char _license[] SEC("license") = "GPL";

samples/bpf/xdp_adjust_tail_user.c

0 → 100644

+142 −0

Original line number	Diff line number	Diff line
		/* SPDX-License-Identifier: GPL-2.0
		* Copyright (c) 2018 Facebook
		*
		* This program is free software; you can redistribute it and/or
		* modify it under the terms of version 2 of the GNU General Public
		* License as published by the Free Software Foundation.
		*/
		#include <linux/bpf.h>
		#include <linux/if_link.h>
		#include <assert.h>
		#include <errno.h>
		#include <signal.h>
		#include <stdio.h>
		#include <stdlib.h>
		#include <string.h>
		#include <sys/resource.h>
		#include <arpa/inet.h>
		#include <netinet/ether.h>
		#include <unistd.h>
		#include <time.h>
		#include "bpf_load.h"
		#include "libbpf.h"
		#include "bpf_util.h"

		#define STATS_INTERVAL_S 2U

		static int ifindex = -1;
		static __u32 xdp_flags;

		static void int_exit(int sig)
		{
		if (ifindex > -1)
		bpf_set_link_xdp_fd(ifindex, -1, xdp_flags);
		exit(0);
		}

		/* simple "icmp packet too big sent" counter
		*/
		static void poll_stats(unsigned int kill_after_s)
		{
		time_t started_at = time(NULL);
		__u64 value = 0;
		int key = 0;


		while (!kill_after_s \|\| time(NULL) - started_at <= kill_after_s) {
		sleep(STATS_INTERVAL_S);

		assert(bpf_map_lookup_elem(map_fd[0], &key, &value) == 0);

		printf("icmp \"packet too big\" sent: %10llu pkts\n", value);
		}
		}

		static void usage(const char *cmd)
		{
		printf("Start a XDP prog which send ICMP \"packet too big\" \n"
		"messages if ingress packet is bigger then MAX_SIZE bytes\n");
		printf("Usage: %s [...]\n", cmd);
		printf(" -i <ifindex> Interface Index\n");
		printf(" -T <stop-after-X-seconds> Default: 0 (forever)\n");
		printf(" -S use skb-mode\n");
		printf(" -N enforce native mode\n");
		printf(" -h Display this help\n");
		}

		int main(int argc, char **argv)
		{
		unsigned char opt_flags[256] = {};
		unsigned int kill_after_s = 0;
		const char *optstr = "i:T:SNh";
		struct rlimit r = {RLIM_INFINITY, RLIM_INFINITY};
		char filename[256];
		int opt;
		int i;


		for (i = 0; i < strlen(optstr); i++)
		if (optstr[i] != 'h' && 'a' <= optstr[i] && optstr[i] <= 'z')
		opt_flags[(unsigned char)optstr[i]] = 1;

		while ((opt = getopt(argc, argv, optstr)) != -1) {

		switch (opt) {
		case 'i':
		ifindex = atoi(optarg);
		break;
		case 'T':
		kill_after_s = atoi(optarg);
		break;
		case 'S':
		xdp_flags \|= XDP_FLAGS_SKB_MODE;
		break;
		case 'N':
		xdp_flags \|= XDP_FLAGS_DRV_MODE;
		break;
		default:
		usage(argv[0]);
		return 1;
		}
		opt_flags[opt] = 0;
		}

		for (i = 0; i < strlen(optstr); i++) {
		if (opt_flags[(unsigned int)optstr[i]]) {
		fprintf(stderr, "Missing argument -%c\n", optstr[i]);
		usage(argv[0]);
		return 1;
		}
		}

		if (setrlimit(RLIMIT_MEMLOCK, &r)) {
		perror("setrlimit(RLIMIT_MEMLOCK, RLIM_INFINITY)");
		return 1;
		}

		snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);

		if (load_bpf_file(filename)) {
		printf("%s", bpf_log_buf);
		return 1;
		}

		if (!prog_fd[0]) {
		printf("load_bpf_file: %s\n", strerror(errno));
		return 1;
		}

		signal(SIGINT, int_exit);
		signal(SIGTERM, int_exit);

		if (bpf_set_link_xdp_fd(ifindex, prog_fd[0], xdp_flags) < 0) {
		printf("link set xdp fd failed\n");
		return 1;
		}

		poll_stats(kill_after_s);

		bpf_set_link_xdp_fd(ifindex, -1, xdp_flags);

		return 0;
		}

tools/testing/selftests/bpf/bpf_helpers.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -132,6 +132,8 @@ static int (bpf_l3_csum_replace)(void ctx, int off, int from, int to, int flag
		(void *) BPF_FUNC_l3_csum_replace;
		static int (bpf_l4_csum_replace)(void ctx, int off, int from, int to, int flags) =
		(void *) BPF_FUNC_l4_csum_replace;
		static int (bpf_csum_diff)(void from, int from_size, void *to, int to_size, int seed) =
		(void *) BPF_FUNC_csum_diff;
		static int (bpf_skb_under_cgroup)(void ctx, void *map, int index) =
		(void *) BPF_FUNC_skb_under_cgroup;
		static int (bpf_skb_change_head)(void , int len, int flags) =

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