txring_overwrite.c

  1// SPDX-License-Identifier: GPL-2.0
  2
  3/*
  4 * Verify that consecutive sends over packet tx_ring are mirrored
  5 * with their original content intact.
  6 */
  7
  8#define _GNU_SOURCE
  9
 10#include <arpa/inet.h>
 11#include <assert.h>
 12#include <error.h>
 13#include <errno.h>
 14#include <fcntl.h>
 15#include <linux/filter.h>
 16#include <linux/if_packet.h>
 17#include <net/ethernet.h>
 18#include <net/if.h>
 19#include <netinet/in.h>
 20#include <netinet/ip.h>
 21#include <netinet/udp.h>
 22#include <poll.h>
 23#include <pthread.h>
 24#include <sched.h>
 25#include <sys/ioctl.h>
 26#include <sys/mman.h>
 27#include <sys/socket.h>
 28#include <sys/time.h>
 29#include <sys/types.h>
 30#include <sys/utsname.h>
 31#include <stdbool.h>
 32#include <stdint.h>
 33#include <stdio.h>
 34#include <stdlib.h>
 35#include <string.h>
 36#include <unistd.h>
 37
 38const int eth_off = TPACKET_HDRLEN - sizeof(struct sockaddr_ll);
 39const int cfg_frame_size = 1000;
 40
 41static void build_packet(void *buffer, size_t blen, char payload_char)
 42{
 43	struct udphdr *udph;
 44	struct ethhdr *eth;
 45	struct iphdr *iph;
 46	size_t off = 0;
 47
 48	memset(buffer, 0, blen);
 49
 50	eth = buffer;
 51	eth->h_proto = htons(ETH_P_IP);
 52
 53	off += sizeof(*eth);
 54	iph = buffer + off;
 55	iph->ttl	= 8;
 56	iph->ihl	= 5;
 57	iph->version	= 4;
 58	iph->saddr	= htonl(INADDR_LOOPBACK);
 59	iph->daddr	= htonl(INADDR_LOOPBACK + 1);
 60	iph->protocol	= IPPROTO_UDP;
 61	iph->tot_len	= htons(blen - off);
 62	iph->check	= 0;
 63
 64	off += sizeof(*iph);
 65	udph = buffer + off;
 66	udph->dest	= htons(8000);
 67	udph->source	= htons(8001);
 68	udph->len	= htons(blen - off);
 69	udph->check	= 0;
 70
 71	off += sizeof(*udph);
 72	memset(buffer + off, payload_char, blen - off);
 73}
 74
 75static int setup_rx(void)
 76{
 77	int fdr;
 78
 79	fdr = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_IP));
 80	if (fdr == -1)
 81		error(1, errno, "socket r");
 82
 83	return fdr;
 84}
 85
 86static int setup_tx(char **ring)
 87{
 88	struct sockaddr_ll laddr = {};
 89	struct tpacket_req req = {};
 90	int fdt;
 91
 92	fdt = socket(PF_PACKET, SOCK_RAW, 0);
 93	if (fdt == -1)
 94		error(1, errno, "socket t");
 95
 96	laddr.sll_family = AF_PACKET;
 97	laddr.sll_protocol = htons(0);
 98	laddr.sll_ifindex = if_nametoindex("lo");
 99	if (!laddr.sll_ifindex)
100		error(1, errno, "if_nametoindex");
101
102	if (bind(fdt, (void *)&laddr, sizeof(laddr)))
103		error(1, errno, "bind fdt");
104
105	req.tp_block_size = getpagesize();
106	req.tp_block_nr   = 1;
107	req.tp_frame_size = getpagesize();
108	req.tp_frame_nr   = 1;
109
110	if (setsockopt(fdt, SOL_PACKET, PACKET_TX_RING,
111		       (void *)&req, sizeof(req)))
112		error(1, errno, "setsockopt ring");
113
114	*ring = mmap(0, req.tp_block_size * req.tp_block_nr,
115		     PROT_READ | PROT_WRITE, MAP_SHARED, fdt, 0);
116	if (*ring == MAP_FAILED)
117		error(1, errno, "mmap");
118
119	return fdt;
120}
121
122static void send_pkt(int fdt, void *slot, char payload_char)
123{
124	struct tpacket_hdr *header = slot;
125	int ret;
126
127	while (header->tp_status != TP_STATUS_AVAILABLE)
128		usleep(1000);
129
130	build_packet(slot + eth_off, cfg_frame_size, payload_char);
131
132	header->tp_len = cfg_frame_size;
133	header->tp_status = TP_STATUS_SEND_REQUEST;
134
135	ret = sendto(fdt, NULL, 0, 0, NULL, 0);
136	if (ret == -1)
137		error(1, errno, "kick tx");
138}
139
140static int read_verify_pkt(int fdr, char payload_char)
141{
142	char buf[100];
143	int ret;
144
145	ret = read(fdr, buf, sizeof(buf));
146	if (ret != sizeof(buf))
147		error(1, errno, "read");
148
149	if (buf[60] != payload_char) {
150		printf("wrong pattern: 0x%x != 0x%x\n", buf[60], payload_char);
151		return 1;
152	}
153
154	printf("read: %c (0x%x)\n", buf[60], buf[60]);
155	return 0;
156}
157
158int main(int argc, char **argv)
159{
160	const char payload_patterns[] = "ab";
161	char *ring;
162	int fdr, fdt, ret = 0;
163
164	fdr = setup_rx();
165	fdt = setup_tx(&ring);
166
167	send_pkt(fdt, ring, payload_patterns[0]);
168	send_pkt(fdt, ring, payload_patterns[1]);
169
170	ret |= read_verify_pkt(fdr, payload_patterns[0]);
171	ret |= read_verify_pkt(fdr, payload_patterns[1]);
172
173	if (close(fdt))
174		error(1, errno, "close t");
175	if (close(fdr))
176		error(1, errno, "close r");
177
178	return ret;
179}