tools/testing/selftests/net/gro.c

// SPDX-License-Identifier: GPL-2.0
/*
 * This testsuite provides conformance testing for GRO coalescing.
 *
 * Test cases:
 * 1.data
 *  Data packets of the same size and same header setup with correct
 *  sequence numbers coalesce. The one exception being the last data
 *  packet coalesced: it can be smaller than the rest and coalesced
 *  as long as it is in the same flow.
 * 2.ack
 *  Pure ACK does not coalesce.
 * 3.flags
 *  Specific test cases: no packets with PSH, SYN, URG, RST set will
 *  be coalesced.
 * 4.tcp
 *  Packets with incorrect checksum, non-consecutive seqno and
 *  different TCP header options shouldn't coalesce. Nit: given that
 *  some extension headers have paddings, such as timestamp, headers
 *  that are padding differently would not be coalesced.
 * 5.ip:
 *  Packets with different (ECN, TTL, TOS) header, ip options or
 *  ip fragments (ipv6) shouldn't coalesce.
 * 6.large:
 *  Packets larger than GRO_MAX_SIZE packets shouldn't coalesce.
 *
 * MSS is defined as 4096 - header because if it is too small
 * (i.e. 1500 MTU - header), it will result in many packets,
 * increasing the "large" test case's flakiness. This is because
 * due to time sensitivity in the coalescing window, the receiver
 * may not coalesce all of the packets.
 *
 * Note the timing issue applies to all of the test cases, so some
 * flakiness is to be expected.
 *
 */

#define _GNU_SOURCE

#include <arpa/inet.h>
#include <errno.h>
#include <error.h>
#include <getopt.h>
#include <linux/filter.h>
#include <linux/if_packet.h>
#include <linux/ipv6.h>
#include <net/ethernet.h>
#include <net/if.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/ip6.h>
#include <netinet/tcp.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdio.h>
#include <stdarg.h>
#include <string.h>
#include <unistd.h>

#include "../kselftest.h"

#define DPORT 8000
#define SPORT 1500
#define PAYLOAD_LEN 100
#define NUM_PACKETS 4
#define START_SEQ 100
#define START_ACK 100
#define ETH_P_NONE 0
#define TOTAL_HDR_LEN (ETH_HLEN + sizeof(struct ipv6hdr) + sizeof(struct tcphdr))
#define MSS (4096 - sizeof(struct tcphdr) - sizeof(struct ipv6hdr))
#define MAX_PAYLOAD (IP_MAXPACKET - sizeof(struct tcphdr) - sizeof(struct ipv6hdr))
#define NUM_LARGE_PKT (MAX_PAYLOAD / MSS)
#define MAX_HDR_LEN (ETH_HLEN + sizeof(struct ipv6hdr) + sizeof(struct tcphdr))
#define MIN_EXTHDR_SIZE 8
#define EXT_PAYLOAD_1 "\x00\x00\x00\x00\x00\x00"
#define EXT_PAYLOAD_2 "\x11\x11\x11\x11\x11\x11"

#define ipv6_optlen(p)  (((p)->hdrlen+1) << 3) /* calculate IPv6 extension header len */
#define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2*!!(condition)]))

static const char *addr6_src = "fdaa::2";
static const char *addr6_dst = "fdaa::1";
static const char *addr4_src = "192.168.1.200";
static const char *addr4_dst = "192.168.1.100";
static int proto = -1;
static uint8_t src_mac[ETH_ALEN], dst_mac[ETH_ALEN];
static char *testname = "data";
static char *ifname = "eth0";
static char *smac = "aa:00:00:00:00:02";
static char *dmac = "aa:00:00:00:00:01";
static bool verbose;
static bool tx_socket = true;
static int tcp_offset = -1;
static int total_hdr_len = -1;
static int ethhdr_proto = -1;
static const int num_flush_id_cases = 6;

static void vlog(const char *fmt, ...)
{
	va_list args;

	if (verbose) {
		va_start(args, fmt);
		vfprintf(stderr, fmt, args);
		va_end(args);
	}
}

static void setup_sock_filter(int fd)
{
	const int dport_off = tcp_offset + offsetof(struct tcphdr, dest);
	const int ethproto_off = offsetof(struct ethhdr, h_proto);
	int optlen = 0;
	int ipproto_off, opt_ipproto_off;
	int next_off;

	if (proto == PF_INET)
		next_off = offsetof(struct iphdr, protocol);
	else
		next_off = offsetof(struct ipv6hdr, nexthdr);
	ipproto_off = ETH_HLEN + next_off;

	/* Overridden later if exthdrs are used: */
	opt_ipproto_off = ipproto_off;

	if (strcmp(testname, "ip") == 0) {
		if (proto == PF_INET)
			optlen = sizeof(struct ip_timestamp);
		else {
			BUILD_BUG_ON(sizeof(struct ip6_hbh) > MIN_EXTHDR_SIZE);
			BUILD_BUG_ON(sizeof(struct ip6_dest) > MIN_EXTHDR_SIZE);
			BUILD_BUG_ON(sizeof(struct ip6_frag) > MIN_EXTHDR_SIZE);

			/* same size for HBH and Fragment extension header types */
			optlen = MIN_EXTHDR_SIZE;
			opt_ipproto_off = ETH_HLEN + sizeof(struct ipv6hdr)
				+ offsetof(struct ip6_ext, ip6e_nxt);
		}
	}

	/* this filter validates the following:
	 *	- packet is IPv4/IPv6 according to the running test.
	 *	- packet is TCP. Also handles the case of one extension header and then TCP.
	 *	- checks the packet tcp dport equals to DPORT. Also handles the case of one
	 *	  extension header and then TCP.
	 */
	struct sock_filter filter[] = {
			BPF_STMT(BPF_LD  + BPF_H   + BPF_ABS, ethproto_off),
			BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ntohs(ethhdr_proto), 0, 9),
			BPF_STMT(BPF_LD  + BPF_B   + BPF_ABS, ipproto_off),
			BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_TCP, 2, 0),
			BPF_STMT(BPF_LD  + BPF_B   + BPF_ABS, opt_ipproto_off),
			BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_TCP, 0, 5),
			BPF_STMT(BPF_LD  + BPF_H   + BPF_ABS, dport_off),
			BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, DPORT, 2, 0),
			BPF_STMT(BPF_LD  + BPF_H   + BPF_ABS, dport_off + optlen),
			BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, DPORT, 0, 1),
			BPF_STMT(BPF_RET + BPF_K, 0xFFFFFFFF),
			BPF_STMT(BPF_RET + BPF_K, 0),
	};

	struct sock_fprog bpf = {
		.len = ARRAY_SIZE(filter),
		.filter = filter,
	};

	if (setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, &bpf, sizeof(bpf)) < 0)
		error(1, errno, "error setting filter");
}

static uint32_t checksum_nofold(void *data, size_t len, uint32_t sum)
{
	uint16_t *words = data;
	int i;

	for (i = 0; i < len / 2; i++)
		sum += words[i];
	if (len & 1)
		sum += ((char *)data)[len - 1];
	return sum;
}

static uint16_t checksum_fold(void *data, size_t len, uint32_t sum)
{
	sum = checksum_nofold(data, len, sum);
	while (sum > 0xFFFF)
		sum = (sum & 0xFFFF) + (sum >> 16);
	return ~sum;
}

static uint16_t tcp_checksum(void *buf, int payload_len)
{
	struct pseudo_header6 {
		struct in6_addr saddr;
		struct in6_addr daddr;
		uint16_t protocol;
		uint16_t payload_len;
	} ph6;
	struct pseudo_header4 {
		struct in_addr saddr;
		struct in_addr daddr;
		uint16_t protocol;
		uint16_t payload_len;
	} ph4;
	uint32_t sum = 0;

	if (proto == PF_INET6) {
		if (inet_pton(AF_INET6, addr6_src, &ph6.saddr) != 1)
			error(1, errno, "inet_pton6 source ip pseudo");
		if (inet_pton(AF_INET6, addr6_dst, &ph6.daddr) != 1)
			error(1, errno, "inet_pton6 dest ip pseudo");
		ph6.protocol = htons(IPPROTO_TCP);
		ph6.payload_len = htons(sizeof(struct tcphdr) + payload_len);

		sum = checksum_nofold(&ph6, sizeof(ph6), 0);
	} else if (proto == PF_INET) {
		if (inet_pton(AF_INET, addr4_src, &ph4.saddr) != 1)
			error(1, errno, "inet_pton source ip pseudo");
		if (inet_pton(AF_INET, addr4_dst, &ph4.daddr) != 1)
			error(1, errno, "inet_pton dest ip pseudo");
		ph4.protocol = htons(IPPROTO_TCP);
		ph4.payload_len = htons(sizeof(struct tcphdr) + payload_len);

		sum = checksum_nofold(&ph4, sizeof(ph4), 0);
	}

	return checksum_fold(buf, sizeof(struct tcphdr) + payload_len, sum);
}

static void read_MAC(uint8_t *mac_addr, char *mac)
{
	if (sscanf(mac, "%hhx:%hhx:%hhx:%hhx:%hhx:%hhx",
		   &mac_addr[0], &mac_addr[1], &mac_addr[2],
		   &mac_addr[3], &mac_addr[4], &mac_addr[5]) != 6)
		error(1, 0, "sscanf");
}

static void fill_datalinklayer(void *buf)
{
	struct ethhdr *eth = buf;

	memcpy(eth->h_dest, dst_mac, ETH_ALEN);
	memcpy(eth->h_source, src_mac, ETH_ALEN);
	eth->h_proto = ethhdr_proto;
}

static void fill_networklayer(void *buf, int payload_len)
{
	struct ipv6hdr *ip6h = buf;
	struct iphdr *iph = buf;

	if (proto == PF_INET6) {
		memset(ip6h, 0, sizeof(*ip6h));

		ip6h->version = 6;
		ip6h->payload_len = htons(sizeof(struct tcphdr) + payload_len);
		ip6h->nexthdr = IPPROTO_TCP;
		ip6h->hop_limit = 8;
		if (inet_pton(AF_INET6, addr6_src, &ip6h->saddr) != 1)
			error(1, errno, "inet_pton source ip6");
		if (inet_pton(AF_INET6, addr6_dst, &ip6h->daddr) != 1)
			error(1, errno, "inet_pton dest ip6");
	} else if (proto == PF_INET) {
		memset(iph, 0, sizeof(*iph));

		iph->version = 4;
		iph->ihl = 5;
		iph->ttl = 8;
		iph->protocol	= IPPROTO_TCP;
		iph->tot_len = htons(sizeof(struct tcphdr) +
				payload_len + sizeof(struct iphdr));
		iph->frag_off = htons(0x4000); /* DF = 1, MF = 0 */
		if (inet_pton(AF_INET, addr4_src, &iph->saddr) != 1)
			error(1, errno, "inet_pton source ip");
		if (inet_pton(AF_INET, addr4_dst, &iph->daddr) != 1)
			error(1, errno, "inet_pton dest ip");
		iph->check = checksum_fold(buf, sizeof(struct iphdr), 0);
	}
}

static void fill_transportlayer(void *buf, int seq_offset, int ack_offset,
				int payload_len, int fin)
{
	struct tcphdr *tcph = buf;

	memset(tcph, 0, sizeof(*tcph));

	tcph->source = htons(SPORT);
	tcph->dest = htons(DPORT);
	tcph->seq = ntohl(START_SEQ + seq_offset);
	tcph->ack_seq = ntohl(START_ACK + ack_offset);
	tcph->ack = 1;
	tcph->fin = fin;
	tcph->doff = 5;
	tcph->window = htons(TCP_MAXWIN);
	tcph->urg_ptr = 0;
	tcph->check = tcp_checksum(tcph, payload_len);
}

static void write_packet(int fd, char *buf, int len, struct sockaddr_ll *daddr)
{
	int ret = -1;

	ret = sendto(fd, buf, len, 0, (struct sockaddr *)daddr, sizeof(*daddr));
	if (ret == -1)
		error(1, errno, "sendto failure");
	if (ret != len)
		error(1, errno, "sendto wrong length");
}

static void create_packet(void *buf, int seq_offset, int ack_offset,
			  int payload_len, int fin)
{
	memset(buf, 0, total_hdr_len);
	memset(buf + total_hdr_len, 'a', payload_len);
	fill_transportlayer(buf + tcp_offset, seq_offset, ack_offset,
			    payload_len, fin);
	fill_networklayer(buf + ETH_HLEN, payload_len);
	fill_datalinklayer(buf);
}

/* send one extra flag, not first and not last pkt */
static void send_flags(int fd, struct sockaddr_ll *daddr, int psh, int syn,
		       int rst, int urg)
{
	static char flag_buf[MAX_HDR_LEN + PAYLOAD_LEN];
	static char buf[MAX_HDR_LEN + PAYLOAD_LEN];
	int payload_len, pkt_size, flag, i;
	struct tcphdr *tcph;

	payload_len = PAYLOAD_LEN * psh;
	pkt_size = total_hdr_len + payload_len;
	flag = NUM_PACKETS / 2;

	create_packet(flag_buf, flag * payload_len, 0, payload_len, 0);

	tcph = (struct tcphdr *)(flag_buf + tcp_offset);
	tcph->psh = psh;
	tcph->syn = syn;
	tcph->rst = rst;
	tcph->urg = urg;
	tcph->check = 0;
	tcph->check = tcp_checksum(tcph, payload_len);

	for (i = 0; i < NUM_PACKETS + 1; i++) {
		if (i == flag) {
			write_packet(fd, flag_buf, pkt_size, daddr);
			continue;
		}
		create_packet(buf, i * PAYLOAD_LEN, 0, PAYLOAD_LEN, 0);
		write_packet(fd, buf, total_hdr_len + PAYLOAD_LEN, daddr);
	}
}

/* Test for data of same length, smaller than previous
 * and of different lengths
 */
static void send_data_pkts(int fd, struct sockaddr_ll *daddr,
			   int payload_len1, int payload_len2)
{
	static char buf[ETH_HLEN + IP_MAXPACKET];

	create_packet(buf, 0, 0, payload_len1, 0);
	write_packet(fd, buf, total_hdr_len + payload_len1, daddr);
	create_packet(buf, payload_len1, 0, payload_len2, 0);
	write_packet(fd, buf, total_hdr_len + payload_len2, daddr);
}

/* If incoming segments make tracked segment length exceed
 * legal IP datagram length, do not coalesce
 */
static void send_large(int fd, struct sockaddr_ll *daddr, int remainder)
{
	static char pkts[NUM_LARGE_PKT][TOTAL_HDR_LEN + MSS];
	static char last[TOTAL_HDR_LEN + MSS];
	static char new_seg[TOTAL_HDR_LEN + MSS];
	int i;

	for (i = 0; i < NUM_LARGE_PKT; i++)
		create_packet(pkts[i], i * MSS, 0, MSS, 0);
	create_packet(last, NUM_LARGE_PKT * MSS, 0, remainder, 0);
	create_packet(new_seg, (NUM_LARGE_PKT + 1) * MSS, 0, remainder, 0);

	for (i = 0; i < NUM_LARGE_PKT; i++)
		write_packet(fd, pkts[i], total_hdr_len + MSS, daddr);
	write_packet(fd, last, total_hdr_len + remainder, daddr);
	write_packet(fd, new_seg, total_hdr_len + remainder, daddr);
}

/* Pure acks and dup acks don't coalesce */
static void send_ack(int fd, struct sockaddr_ll *daddr)
{
	static char buf[MAX_HDR_LEN];

	create_packet(buf, 0, 0, 0, 0);
	write_packet(fd, buf, total_hdr_len, daddr);
	write_packet(fd, buf, total_hdr_len, daddr);
	create_packet(buf, 0, 1, 0, 0);
	write_packet(fd, buf, total_hdr_len, daddr);
}

static void recompute_packet(char *buf, char *no_ext, int extlen)
{
	struct tcphdr *tcphdr = (struct tcphdr *)(buf + tcp_offset);
	struct ipv6hdr *ip6h = (struct ipv6hdr *)(buf + ETH_HLEN);
	struct iphdr *iph = (struct iphdr *)(buf + ETH_HLEN);

	memmove(buf, no_ext, total_hdr_len);
	memmove(buf + total_hdr_len + extlen,
		no_ext + total_hdr_len, PAYLOAD_LEN);

	tcphdr->doff = tcphdr->doff + (extlen / 4);
	tcphdr->check = 0;
	tcphdr->check = tcp_checksum(tcphdr, PAYLOAD_LEN + extlen);
	if (proto == PF_INET) {
		iph->tot_len = htons(ntohs(iph->tot_len) + extlen);
		iph->check = 0;
		iph->check = checksum_fold(iph, sizeof(struct iphdr), 0);
	} else {
		ip6h->payload_len = htons(ntohs(ip6h->payload_len) + extlen);
	}
}

static void tcp_write_options(char *buf, int kind, int ts)
{
	struct tcp_option_ts {
		uint8_t kind;
		uint8_t len;
		uint32_t tsval;
		uint32_t tsecr;
	} *opt_ts = (void *)buf;
	struct tcp_option_window {
		uint8_t kind;
		uint8_t len;
		uint8_t shift;
	} *opt_window = (void *)buf;

	switch (kind) {
	case TCPOPT_NOP:
		buf[0] = TCPOPT_NOP;
		break;
	case TCPOPT_WINDOW:
		memset(opt_window, 0, sizeof(struct tcp_option_window));
		opt_window->kind = TCPOPT_WINDOW;
		opt_window->len = TCPOLEN_WINDOW;
		opt_window->shift = 0;
		break;
	case TCPOPT_TIMESTAMP:
		memset(opt_ts, 0, sizeof(struct tcp_option_ts));
		opt_ts->kind = TCPOPT_TIMESTAMP;
		opt_ts->len = TCPOLEN_TIMESTAMP;
		opt_ts->tsval = ts;
		opt_ts->tsecr = 0;
		break;
	default:
		error(1, 0, "unimplemented TCP option");
		break;
	}
}

/* TCP with options is always a permutation of {TS, NOP, NOP}.
 * Implement different orders to verify coalescing stops.
 */
static void add_standard_tcp_options(char *buf, char *no_ext, int ts, int order)
{
	switch (order) {
	case 0:
		tcp_write_options(buf + total_hdr_len, TCPOPT_NOP, 0);
		tcp_write_options(buf + total_hdr_len + 1, TCPOPT_NOP, 0);
		tcp_write_options(buf + total_hdr_len + 2 /* two NOP opts */,
				  TCPOPT_TIMESTAMP, ts);
		break;
	case 1:
		tcp_write_options(buf + total_hdr_len, TCPOPT_NOP, 0);
		tcp_write_options(buf + total_hdr_len + 1,
				  TCPOPT_TIMESTAMP, ts);
		tcp_write_options(buf + total_hdr_len + 1 + TCPOLEN_TIMESTAMP,
				  TCPOPT_NOP, 0);
		break;
	case 2:
		tcp_write_options(buf + total_hdr_len, TCPOPT_TIMESTAMP, ts);
		tcp_write_options(buf + total_hdr_len + TCPOLEN_TIMESTAMP + 1,
				  TCPOPT_NOP, 0);
		tcp_write_options(buf + total_hdr_len + TCPOLEN_TIMESTAMP + 2,
				  TCPOPT_NOP, 0);
		break;
	default:
		error(1, 0, "unknown order");
		break;
	}
	recompute_packet(buf, no_ext, TCPOLEN_TSTAMP_APPA);
}

/* Packets with invalid checksum don't coalesce. */
static void send_changed_checksum(int fd, struct sockaddr_ll *daddr)
{
	static char buf[MAX_HDR_LEN + PAYLOAD_LEN];
	struct tcphdr *tcph = (struct tcphdr *)(buf + tcp_offset);
	int pkt_size = total_hdr_len + PAYLOAD_LEN;

	create_packet(buf, 0, 0, PAYLOAD_LEN, 0);
	write_packet(fd, buf, pkt_size, daddr);

	create_packet(buf, PAYLOAD_LEN, 0, PAYLOAD_LEN, 0);
	tcph->check = tcph->check - 1;
	write_packet(fd, buf, pkt_size, daddr);
}

 /* Packets with non-consecutive sequence number don't coalesce.*/
static void send_changed_seq(int fd, struct sockaddr_ll *daddr)
{
	static char buf[MAX_HDR_LEN + PAYLOAD_LEN];
	struct tcphdr *tcph = (struct tcphdr *)(buf + tcp_offset);
	int pkt_size = total_hdr_len + PAYLOAD_LEN;

	create_packet(buf, 0, 0, PAYLOAD_LEN, 0);
	write_packet(fd, buf, pkt_size, daddr);

	create_packet(buf, PAYLOAD_LEN, 0, PAYLOAD_LEN, 0);
	tcph->seq = ntohl(htonl(tcph->seq) + 1);
	tcph->check = 0;
	tcph->check = tcp_checksum(tcph, PAYLOAD_LEN);
	write_packet(fd, buf, pkt_size, daddr);
}

 /* Packet with different timestamp option or different timestamps
  * don't coalesce.
  */
static void send_changed_ts(int fd, struct sockaddr_ll *daddr)
{
	static char buf[MAX_HDR_LEN + PAYLOAD_LEN];
	static char extpkt[sizeof(buf) + TCPOLEN_TSTAMP_APPA];
	int pkt_size = total_hdr_len + PAYLOAD_LEN + TCPOLEN_TSTAMP_APPA;

	create_packet(buf, 0, 0, PAYLOAD_LEN, 0);
	add_standard_tcp_options(extpkt, buf, 0, 0);
	write_packet(fd, extpkt, pkt_size, daddr);

	create_packet(buf, PAYLOAD_LEN, 0, PAYLOAD_LEN, 0);
	add_standard_tcp_options(extpkt, buf, 0, 0);
	write_packet(fd, extpkt, pkt_size, daddr);

	create_packet(buf, PAYLOAD_LEN * 2, 0, PAYLOAD_LEN, 0);
	add_standard_tcp_options(extpkt, buf, 100, 0);
	write_packet(fd, extpkt, pkt_size, daddr);

	create_packet(buf, PAYLOAD_LEN * 3, 0, PAYLOAD_LEN, 0);
	add_standard_tcp_options(extpkt, buf, 100, 1);
	write_packet(fd, extpkt, pkt_size, daddr);

	create_packet(buf, PAYLOAD_LEN * 4, 0, PAYLOAD_LEN, 0);
	add_standard_tcp_options(extpkt, buf, 100, 2);
	write_packet(fd, extpkt, pkt_size, daddr);
}

/* Packet with different tcp options don't coalesce. */
static void send_diff_opt(int fd, struct sockaddr_ll *daddr)
{
	static char buf[MAX_HDR_LEN + PAYLOAD_LEN];
	static char extpkt1[sizeof(buf) + TCPOLEN_TSTAMP_APPA];
	static char extpkt2[sizeof(buf) + TCPOLEN_MAXSEG];
	int extpkt1_size = total_hdr_len + PAYLOAD_LEN + TCPOLEN_TSTAMP_APPA;
	int extpkt2_size = total_hdr_len + PAYLOAD_LEN + TCPOLEN_MAXSEG;

	create_packet(buf, 0, 0, PAYLOAD_LEN, 0);
	add_standard_tcp_options(extpkt1, buf, 0, 0);
	write_packet(fd, extpkt1, extpkt1_size, daddr);

	create_packet(buf, PAYLOAD_LEN, 0, PAYLOAD_LEN, 0);
	add_standard_tcp_options(extpkt1, buf, 0, 0);
	write_packet(fd, extpkt1, extpkt1_size, daddr);

	create_packet(buf, PAYLOAD_LEN * 2, 0, PAYLOAD_LEN, 0);
	tcp_write_options(extpkt2 + MAX_HDR_LEN, TCPOPT_NOP, 0);
	tcp_write_options(extpkt2 + MAX_HDR_LEN + 1, TCPOPT_WINDOW, 0);
	recompute_packet(extpkt2, buf, TCPOLEN_WINDOW + 1);
	write_packet(fd, extpkt2, extpkt2_size, daddr);
}

static void add_ipv4_ts_option(void *buf, void *optpkt)
{
	struct ip_timestamp *ts = (struct ip_timestamp *)(optpkt + tcp_offset);
	int optlen = sizeof(struct ip_timestamp);
	struct iphdr *iph;

	if (optlen % 4)
		error(1, 0, "ipv4 timestamp length is not a multiple of 4B");

	ts->ipt_code = IPOPT_TS;
	ts->ipt_len = optlen;
	ts->ipt_ptr = 5;
	ts->ipt_flg = IPOPT_TS_TSONLY;

	memcpy(optpkt, buf, tcp_offset);
	memcpy(optpkt + tcp_offset + optlen, buf + tcp_offset,
	       sizeof(struct tcphdr) + PAYLOAD_LEN);

	iph = (struct iphdr *)(optpkt + ETH_HLEN);
	iph->ihl = 5 + (optlen / 4);
	iph->tot_len = htons(ntohs(iph->tot_len) + optlen);
	iph->check = 0;
	iph->check = checksum_fold(iph, sizeof(struct iphdr) + optlen, 0);
}

static void add_ipv6_exthdr(void *buf, void *optpkt, __u8 exthdr_type, char *ext_payload)
{
	struct ipv6_opt_hdr *exthdr = (struct ipv6_opt_hdr *)(optpkt + tcp_offset);
	struct ipv6hdr *iph = (struct ipv6hdr *)(optpkt + ETH_HLEN);
	char *exthdr_payload_start = (char *)(exthdr + 1);

	exthdr->hdrlen = 0;
	exthdr->nexthdr = IPPROTO_TCP;

	memcpy(exthdr_payload_start, ext_payload, MIN_EXTHDR_SIZE - sizeof(*exthdr));

	memcpy(optpkt, buf, tcp_offset);
	memcpy(optpkt + tcp_offset + MIN_EXTHDR_SIZE, buf + tcp_offset,
		sizeof(struct tcphdr) + PAYLOAD_LEN);

	iph->nexthdr = exthdr_type;
	iph->payload_len = htons(ntohs(iph->payload_len) + MIN_EXTHDR_SIZE);
}

static void fix_ip4_checksum(struct iphdr *iph)
{
	iph->check = 0;
	iph->check = checksum_fold(iph, sizeof(struct iphdr), 0);
}

static void send_flush_id_case(int fd, struct sockaddr_ll *daddr, int tcase)
{
	static char buf1[MAX_HDR_LEN + PAYLOAD_LEN];
	static char buf2[MAX_HDR_LEN + PAYLOAD_LEN];
	static char buf3[MAX_HDR_LEN + PAYLOAD_LEN];
	bool send_three = false;
	struct iphdr *iph1;
	struct iphdr *iph2;
	struct iphdr *iph3;

	iph1 = (struct iphdr *)(buf1 + ETH_HLEN);
	iph2 = (struct iphdr *)(buf2 + ETH_HLEN);
	iph3 = (struct iphdr *)(buf3 + ETH_HLEN);

	create_packet(buf1, 0, 0, PAYLOAD_LEN, 0);
	create_packet(buf2, PAYLOAD_LEN, 0, PAYLOAD_LEN, 0);
	create_packet(buf3, PAYLOAD_LEN * 2, 0, PAYLOAD_LEN, 0);

	switch (tcase) {
	case 0: /* DF=1, Incrementing - should coalesce */
		iph1->frag_off |= htons(IP_DF);
		iph1->id = htons(8);

		iph2->frag_off |= htons(IP_DF);
		iph2->id = htons(9);
		break;

	case 1: /* DF=1, Fixed - should coalesce */
		iph1->frag_off |= htons(IP_DF);
		iph1->id = htons(8);

		iph2->frag_off |= htons(IP_DF);
		iph2->id = htons(8);
		break;

	case 2: /* DF=0, Incrementing - should coalesce */
		iph1->frag_off &= ~htons(IP_DF);
		iph1->id = htons(8);

		iph2->frag_off &= ~htons(IP_DF);
		iph2->id = htons(9);
		break;

	case 3: /* DF=0, Fixed - should not coalesce */
		iph1->frag_off &= ~htons(IP_DF);
		iph1->id = htons(8);

		iph2->frag_off &= ~htons(IP_DF);
		iph2->id = htons(8);
		break;

	case 4: /* DF=1, two packets incrementing, and one fixed - should
		 * coalesce only the first two packets
		 */
		iph1->frag_off |= htons(IP_DF);
		iph1->id = htons(8);

		iph2->frag_off |= htons(IP_DF);
		iph2->id = htons(9);

		iph3->frag_off |= htons(IP_DF);
		iph3->id = htons(9);
		send_three = true;
		break;

	case 5: /* DF=1, two packets fixed, and one incrementing - should
		 * coalesce only the first two packets
		 */
		iph1->frag_off |= htons(IP_DF);
		iph1->id = htons(8);

		iph2->frag_off |= htons(IP_DF);
		iph2->id = htons(8);

		iph3->frag_off |= htons(IP_DF);
		iph3->id = htons(9);
		send_three = true;
		break;
	}

	fix_ip4_checksum(iph1);
	fix_ip4_checksum(iph2);
	write_packet(fd, buf1, total_hdr_len + PAYLOAD_LEN, daddr);
	write_packet(fd, buf2, total_hdr_len + PAYLOAD_LEN, daddr);

	if (send_three) {
		fix_ip4_checksum(iph3);
		write_packet(fd, buf3, total_hdr_len + PAYLOAD_LEN, daddr);
	}
}

static void test_flush_id(int fd, struct sockaddr_ll *daddr, char *fin_pkt)
{
	for (int i = 0; i < num_flush_id_cases; i++) {
		sleep(1);
		send_flush_id_case(fd, daddr, i);
		sleep(1);
		write_packet(fd, fin_pkt, total_hdr_len, daddr);
	}
}

static void send_ipv6_exthdr(int fd, struct sockaddr_ll *daddr, char *ext_data1, char *ext_data2)
{
	static char buf[MAX_HDR_LEN + PAYLOAD_LEN];
	static char exthdr_pck[sizeof(buf) + MIN_EXTHDR_SIZE];

	create_packet(buf, 0, 0, PAYLOAD_LEN, 0);
	add_ipv6_exthdr(buf, exthdr_pck, IPPROTO_HOPOPTS, ext_data1);
	write_packet(fd, exthdr_pck, total_hdr_len + PAYLOAD_LEN + MIN_EXTHDR_SIZE, daddr);

	create_packet(buf, PAYLOAD_LEN * 1, 0, PAYLOAD_LEN, 0);
	add_ipv6_exthdr(buf, exthdr_pck, IPPROTO_HOPOPTS, ext_data2);
	write_packet(fd, exthdr_pck, total_hdr_len + PAYLOAD_LEN + MIN_EXTHDR_SIZE, daddr);
}

/* IPv4 options shouldn't coalesce */
static void send_ip_options(int fd, struct sockaddr_ll *daddr)
{
	static char buf[MAX_HDR_LEN + PAYLOAD_LEN];
	static char optpkt[sizeof(buf) + sizeof(struct ip_timestamp)];
	int optlen = sizeof(struct ip_timestamp);
	int pkt_size = total_hdr_len + PAYLOAD_LEN + optlen;

	create_packet(buf, 0, 0, PAYLOAD_LEN, 0);
	write_packet(fd, buf, total_hdr_len + PAYLOAD_LEN, daddr);

	create_packet(buf, PAYLOAD_LEN * 1, 0, PAYLOAD_LEN, 0);
	add_ipv4_ts_option(buf, optpkt);
	write_packet(fd, optpkt, pkt_size, daddr);

	create_packet(buf, PAYLOAD_LEN * 2, 0, PAYLOAD_LEN, 0);
	write_packet(fd, buf, total_hdr_len + PAYLOAD_LEN, daddr);
}

/*  IPv4 fragments shouldn't coalesce */
static void send_fragment4(int fd, struct sockaddr_ll *daddr)
{
	static char buf[IP_MAXPACKET];
	struct iphdr *iph = (struct iphdr *)(buf + ETH_HLEN);
	int pkt_size = total_hdr_len + PAYLOAD_LEN;

	create_packet(buf, 0, 0, PAYLOAD_LEN, 0);
	write_packet(fd, buf, pkt_size, daddr);

	/* Once fragmented, packet would retain the total_len.
	 * Tcp header is prepared as if rest of data is in follow-up frags,
	 * but follow up frags aren't actually sent.
	 */
	memset(buf + total_hdr_len, 'a', PAYLOAD_LEN * 2);
	fill_transportlayer(buf + tcp_offset, PAYLOAD_LEN, 0, PAYLOAD_LEN * 2, 0);
	fill_networklayer(buf + ETH_HLEN, PAYLOAD_LEN);
	fill_datalinklayer(buf);

	iph->frag_off = htons(0x6000); // DF = 1, MF = 1
	iph->check = 0;
	iph->check = checksum_fold(iph, sizeof(struct iphdr), 0);
	write_packet(fd, buf, pkt_size, daddr);
}

/* IPv4 packets with different ttl don't coalesce.*/
static void send_changed_ttl(int fd, struct sockaddr_ll *daddr)
{
	int pkt_size = total_hdr_len + PAYLOAD_LEN;
	static char buf[MAX_HDR_LEN + PAYLOAD_LEN];
	struct iphdr *iph = (struct iphdr *)(buf + ETH_HLEN);

	create_packet(buf, 0, 0, PAYLOAD_LEN, 0);
	write_packet(fd, buf, pkt_size, daddr);

	create_packet(buf, PAYLOAD_LEN, 0, PAYLOAD_LEN, 0);
	iph->ttl = 7;
	iph->check = 0;
	iph->check = checksum_fold(iph, sizeof(struct iphdr), 0);
	write_packet(fd, buf, pkt_size, daddr);
}

/* Packets with different tos don't coalesce.*/
static void send_changed_tos(int fd, struct sockaddr_ll *daddr)
{
	int pkt_size = total_hdr_len + PAYLOAD_LEN;
	static char buf[MAX_HDR_LEN + PAYLOAD_LEN];
	struct iphdr *iph = (struct iphdr *)(buf + ETH_HLEN);
	struct ipv6hdr *ip6h = (struct ipv6hdr *)(buf + ETH_HLEN);

	create_packet(buf, 0, 0, PAYLOAD_LEN, 0);
	write_packet(fd, buf, pkt_size, daddr);

	create_packet(buf, PAYLOAD_LEN, 0, PAYLOAD_LEN, 0);
	if (proto == PF_INET) {
		iph->tos = 1;
		iph->check = 0;
		iph->check = checksum_fold(iph, sizeof(struct iphdr), 0);
	} else if (proto == PF_INET6) {
		ip6h->priority = 0xf;
	}
	write_packet(fd, buf, pkt_size, daddr);
}

/* Packets with different ECN don't coalesce.*/
static void send_changed_ECN(int fd, struct sockaddr_ll *daddr)
{
	int pkt_size = total_hdr_len + PAYLOAD_LEN;
	static char buf[MAX_HDR_LEN + PAYLOAD_LEN];
	struct iphdr *iph = (struct iphdr *)(buf + ETH_HLEN);

	create_packet(buf, 0, 0, PAYLOAD_LEN, 0);
	write_packet(fd, buf, pkt_size, daddr);

	create_packet(buf, PAYLOAD_LEN, 0, PAYLOAD_LEN, 0);
	if (proto == PF_INET) {
		buf[ETH_HLEN + 1] ^= 0x2; // ECN set to 10
		iph->check = 0;
		iph->check = checksum_fold(iph, sizeof(struct iphdr), 0);
	} else {
		buf[ETH_HLEN + 1] ^= 0x20; // ECN set to 10
	}
	write_packet(fd, buf, pkt_size, daddr);
}

/* IPv6 fragments and packets with extensions don't coalesce.*/
static void send_fragment6(int fd, struct sockaddr_ll *daddr)
{
	static char buf[MAX_HDR_LEN + PAYLOAD_LEN];
	static char extpkt[MAX_HDR_LEN + PAYLOAD_LEN +
			   sizeof(struct ip6_frag)];
	struct ipv6hdr *ip6h = (struct ipv6hdr *)(buf + ETH_HLEN);
	struct ip6_frag *frag = (void *)(extpkt + tcp_offset);
	int extlen = sizeof(struct ip6_frag);
	int bufpkt_len = total_hdr_len + PAYLOAD_LEN;
	int extpkt_len = bufpkt_len + extlen;
	int i;

	for (i = 0; i < 2; i++) {
		create_packet(buf, PAYLOAD_LEN * i, 0, PAYLOAD_LEN, 0);
		write_packet(fd, buf, bufpkt_len, daddr);
	}
	sleep(1);
	create_packet(buf, PAYLOAD_LEN * 2, 0, PAYLOAD_LEN, 0);
	memset(extpkt, 0, extpkt_len);

	ip6h->nexthdr = IPPROTO_FRAGMENT;
	ip6h->payload_len = htons(ntohs(ip6h->payload_len) + extlen);
	frag->ip6f_nxt = IPPROTO_TCP;

	memcpy(extpkt, buf, tcp_offset);
	memcpy(extpkt + tcp_offset + extlen, buf + tcp_offset,
	       sizeof(struct tcphdr) + PAYLOAD_LEN);
	write_packet(fd, extpkt, extpkt_len, daddr);

	create_packet(buf, PAYLOAD_LEN * 3, 0, PAYLOAD_LEN, 0);
	write_packet(fd, buf, bufpkt_len, daddr);
}

static void bind_packetsocket(int fd)
{
	struct sockaddr_ll daddr = {};

	daddr.sll_family = AF_PACKET;
	daddr.sll_protocol = ethhdr_proto;
	daddr.sll_ifindex = if_nametoindex(ifname);
	if (daddr.sll_ifindex == 0)
		error(1, errno, "if_nametoindex");

	if (bind(fd, (void *)&daddr, sizeof(daddr)) < 0)
		error(1, errno, "could not bind socket");
}

static void set_timeout(int fd)
{
	struct timeval timeout;

	timeout.tv_sec = 3;
	timeout.tv_usec = 0;
	if (setsockopt(fd, SOL_SOCKET, SO_RCVTIMEO, (char *)&timeout,
		       sizeof(timeout)) < 0)
		error(1, errno, "cannot set timeout, setsockopt failed");
}

static void check_recv_pkts(int fd, int *correct_payload,
			    int correct_num_pkts)
{
	static char buffer[IP_MAXPACKET + ETH_HLEN + 1];
	struct iphdr *iph = (struct iphdr *)(buffer + ETH_HLEN);
	struct ipv6hdr *ip6h = (struct ipv6hdr *)(buffer + ETH_HLEN);
	struct tcphdr *tcph;
	bool bad_packet = false;
	int tcp_ext_len = 0;
	int ip_ext_len = 0;
	int pkt_size = -1;
	int data_len = 0;
	int num_pkt = 0;
	int i;

	vlog("Expected {");
	for (i = 0; i < correct_num_pkts; i++)
		vlog("%d ", correct_payload[i]);
	vlog("}, Total %d packets\nReceived {", correct_num_pkts);

	while (1) {
		ip_ext_len = 0;
		pkt_size = recv(fd, buffer, IP_MAXPACKET + ETH_HLEN + 1, 0);
		if (pkt_size < 0)
			error(1, errno, "could not receive");

		if (iph->version == 4)
			ip_ext_len = (iph->ihl - 5) * 4;
		else if (ip6h->version == 6 && ip6h->nexthdr != IPPROTO_TCP)
			ip_ext_len = MIN_EXTHDR_SIZE;

		tcph = (struct tcphdr *)(buffer + tcp_offset + ip_ext_len);

		if (tcph->fin)
			break;

		tcp_ext_len = (tcph->doff - 5) * 4;
		data_len = pkt_size - total_hdr_len - tcp_ext_len - ip_ext_len;
		/* Min ethernet frame payload is 46(ETH_ZLEN - ETH_HLEN) by RFC 802.3.
		 * Ipv4/tcp packets without at least 6 bytes of data will be padded.
		 * Packet sockets are protocol agnostic, and will not trim the padding.
		 */
		if (pkt_size == ETH_ZLEN && iph->version == 4) {
			data_len = ntohs(iph->tot_len)
				- sizeof(struct tcphdr) - sizeof(struct iphdr);
		}
		vlog("%d ", data_len);
		if (data_len != correct_payload[num_pkt]) {
			vlog("[!=%d]", correct_payload[num_pkt]);
			bad_packet = true;
		}
		num_pkt++;
	}
	vlog("}, Total %d packets.\n", num_pkt);
	if (num_pkt != correct_num_pkts)
		error(1, 0, "incorrect number of packets");
	if (bad_packet)
		error(1, 0, "incorrect packet geometry");

	printf("Test succeeded\n\n");
}

static void gro_sender(void)
{
	static char fin_pkt[MAX_HDR_LEN];
	struct sockaddr_ll daddr = {};
	int txfd = -1;

	txfd = socket(PF_PACKET, SOCK_RAW, IPPROTO_RAW);
	if (txfd < 0)
		error(1, errno, "socket creation");

	memset(&daddr, 0, sizeof(daddr));
	daddr.sll_ifindex = if_nametoindex(ifname);
	if (daddr.sll_ifindex == 0)
		error(1, errno, "if_nametoindex");
	daddr.sll_family = AF_PACKET;
	memcpy(daddr.sll_addr, dst_mac, ETH_ALEN);
	daddr.sll_halen = ETH_ALEN;
	create_packet(fin_pkt, PAYLOAD_LEN * 2, 0, 0, 1);

	if (strcmp(testname, "data") == 0) {
		send_data_pkts(txfd, &daddr, PAYLOAD_LEN, PAYLOAD_LEN);
		write_packet(txfd, fin_pkt, total_hdr_len, &daddr);

		send_data_pkts(txfd, &daddr, PAYLOAD_LEN, PAYLOAD_LEN / 2);
		write_packet(txfd, fin_pkt, total_hdr_len, &daddr);

		send_data_pkts(txfd, &daddr, PAYLOAD_LEN / 2, PAYLOAD_LEN);
		write_packet(txfd, fin_pkt, total_hdr_len, &daddr);
	} else if (strcmp(testname, "ack") == 0) {
		send_ack(txfd, &daddr);
		write_packet(txfd, fin_pkt, total_hdr_len, &daddr);
	} else if (strcmp(testname, "flags") == 0) {
		send_flags(txfd, &daddr, 1, 0, 0, 0);
		write_packet(txfd, fin_pkt, total_hdr_len, &daddr);

		send_flags(txfd, &daddr, 0, 1, 0, 0);
		write_packet(txfd, fin_pkt, total_hdr_len, &daddr);

		send_flags(txfd, &daddr, 0, 0, 1, 0);
		write_packet(txfd, fin_pkt, total_hdr_len, &daddr);

		send_flags(txfd, &daddr, 0, 0, 0, 1);
		write_packet(txfd, fin_pkt, total_hdr_len, &daddr);
	} else if (strcmp(testname, "tcp") == 0) {
		send_changed_checksum(txfd, &daddr);
		write_packet(txfd, fin_pkt, total_hdr_len, &daddr);

		send_changed_seq(txfd, &daddr);
		write_packet(txfd, fin_pkt, total_hdr_len, &daddr);

		send_changed_ts(txfd, &daddr);
		write_packet(txfd, fin_pkt, total_hdr_len, &daddr);

		send_diff_opt(txfd, &daddr);
		write_packet(txfd, fin_pkt, total_hdr_len, &daddr);
	} else if (strcmp(testname, "ip") == 0) {
		send_changed_ECN(txfd, &daddr);
		write_packet(txfd, fin_pkt, total_hdr_len, &daddr);

		send_changed_tos(txfd, &daddr);
		write_packet(txfd, fin_pkt, total_hdr_len, &daddr);
		if (proto == PF_INET) {
			/* Modified packets may be received out of order.
			 * Sleep function added to enforce test boundaries
			 * so that fin pkts are not received prior to other pkts.
			 */
			sleep(1);
			send_changed_ttl(txfd, &daddr);
			write_packet(txfd, fin_pkt, total_hdr_len, &daddr);

			sleep(1);
			send_ip_options(txfd, &daddr);
			sleep(1);
			write_packet(txfd, fin_pkt, total_hdr_len, &daddr);

			sleep(1);
			send_fragment4(txfd, &daddr);
			sleep(1);
			write_packet(txfd, fin_pkt, total_hdr_len, &daddr);

			test_flush_id(txfd, &daddr, fin_pkt);
		} else if (proto == PF_INET6) {
			sleep(1);
			send_fragment6(txfd, &daddr);
			sleep(1);
			write_packet(txfd, fin_pkt, total_hdr_len, &daddr);

			sleep(1);
			/* send IPv6 packets with ext header with same payload */
			send_ipv6_exthdr(txfd, &daddr, EXT_PAYLOAD_1, EXT_PAYLOAD_1);
			sleep(1);
			write_packet(txfd, fin_pkt, total_hdr_len, &daddr);

			sleep(1);
			/* send IPv6 packets with ext header with different payload */
			send_ipv6_exthdr(txfd, &daddr, EXT_PAYLOAD_1, EXT_PAYLOAD_2);
			sleep(1);
			write_packet(txfd, fin_pkt, total_hdr_len, &daddr);
		}
	} else if (strcmp(testname, "large") == 0) {
		/* 20 is the difference between min iphdr size
		 * and min ipv6hdr size. Like MAX_HDR_SIZE,
		 * MAX_PAYLOAD is defined with the larger header of the two.
		 */
		int offset = proto == PF_INET ? 20 : 0;
		int remainder = (MAX_PAYLOAD + offset) % MSS;

		send_large(txfd, &daddr, remainder);
		write_packet(txfd, fin_pkt, total_hdr_len, &daddr);

		send_large(txfd, &daddr, remainder + 1);
		write_packet(txfd, fin_pkt, total_hdr_len, &daddr);
	} else {
		error(1, 0, "Unknown testcase");
	}

	if (close(txfd))
		error(1, errno, "socket close");
}

static void gro_receiver(void)
{
	static int correct_payload[NUM_PACKETS];
	int rxfd = -1;

	rxfd = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_NONE));
	if (rxfd < 0)
		error(1, 0, "socket creation");
	setup_sock_filter(rxfd);
	set_timeout(rxfd);
	bind_packetsocket(rxfd);

	memset(correct_payload, 0, sizeof(correct_payload));

	if (strcmp(testname, "data") == 0) {
		printf("pure data packet of same size: ");
		correct_payload[0] = PAYLOAD_LEN * 2;
		check_recv_pkts(rxfd, correct_payload, 1);

		printf("large data packets followed by a smaller one: ");
		correct_payload[0] = PAYLOAD_LEN * 1.5;
		check_recv_pkts(rxfd, correct_payload, 1);

		printf("small data packets followed by a larger one: ");
		correct_payload[0] = PAYLOAD_LEN / 2;
		correct_payload[1] = PAYLOAD_LEN;
		check_recv_pkts(rxfd, correct_payload, 2);
	} else if (strcmp(testname, "ack") == 0) {
		printf("duplicate ack and pure ack: ");
		check_recv_pkts(rxfd, correct_payload, 3);
	} else if (strcmp(testname, "flags") == 0) {
		correct_payload[0] = PAYLOAD_LEN * 3;
		correct_payload[1] = PAYLOAD_LEN * 2;

		printf("psh flag ends coalescing: ");
		check_recv_pkts(rxfd, correct_payload, 2);

		correct_payload[0] = PAYLOAD_LEN * 2;
		correct_payload[1] = 0;
		correct_payload[2] = PAYLOAD_LEN * 2;
		printf("syn flag ends coalescing: ");
		check_recv_pkts(rxfd, correct_payload, 3);

		printf("rst flag ends coalescing: ");
		check_recv_pkts(rxfd, correct_payload, 3);

		printf("urg flag ends coalescing: ");
		check_recv_pkts(rxfd, correct_payload, 3);
	} else if (strcmp(testname, "tcp") == 0) {
		correct_payload[0] = PAYLOAD_LEN;
		correct_payload[1] = PAYLOAD_LEN;
		correct_payload[2] = PAYLOAD_LEN;
		correct_payload[3] = PAYLOAD_LEN;

		printf("changed checksum does not coalesce: ");
		check_recv_pkts(rxfd, correct_payload, 2);

		printf("Wrong Seq number doesn't coalesce: ");
		check_recv_pkts(rxfd, correct_payload, 2);

		printf("Different timestamp doesn't coalesce: ");
		correct_payload[0] = PAYLOAD_LEN * 2;
		check_recv_pkts(rxfd, correct_payload, 4);

		printf("Different options doesn't coalesce: ");
		correct_payload[0] = PAYLOAD_LEN * 2;
		check_recv_pkts(rxfd, correct_payload, 2);
	} else if (strcmp(testname, "ip") == 0) {
		correct_payload[0] = PAYLOAD_LEN;
		correct_payload[1] = PAYLOAD_LEN;

		printf("different ECN doesn't coalesce: ");
		check_recv_pkts(rxfd, correct_payload, 2);

		printf("different tos doesn't coalesce: ");
		check_recv_pkts(rxfd, correct_payload, 2);

		if (proto == PF_INET) {
			printf("different ttl doesn't coalesce: ");
			check_recv_pkts(rxfd, correct_payload, 2);

			printf("ip options doesn't coalesce: ");
			correct_payload[2] = PAYLOAD_LEN;
			check_recv_pkts(rxfd, correct_payload, 3);

			printf("fragmented ip4 doesn't coalesce: ");
			check_recv_pkts(rxfd, correct_payload, 2);

			/* is_atomic checks */
			printf("DF=1, Incrementing - should coalesce: ");
			correct_payload[0] = PAYLOAD_LEN * 2;
			check_recv_pkts(rxfd, correct_payload, 1);

			printf("DF=1, Fixed - should coalesce: ");
			correct_payload[0] = PAYLOAD_LEN * 2;
			check_recv_pkts(rxfd, correct_payload, 1);

			printf("DF=0, Incrementing - should coalesce: ");
			correct_payload[0] = PAYLOAD_LEN * 2;
			check_recv_pkts(rxfd, correct_payload, 1);

			printf("DF=0, Fixed - should not coalesce: ");
			correct_payload[0] = PAYLOAD_LEN;
			correct_payload[1] = PAYLOAD_LEN;
			check_recv_pkts(rxfd, correct_payload, 2);

			printf("DF=1, 2 Incrementing and one fixed - should coalesce only first 2 packets: ");
			correct_payload[0] = PAYLOAD_LEN * 2;
			correct_payload[1] = PAYLOAD_LEN;
			check_recv_pkts(rxfd, correct_payload, 2);

			printf("DF=1, 2 Fixed and one incrementing - should coalesce only first 2 packets: ");
			correct_payload[0] = PAYLOAD_LEN * 2;
			correct_payload[1] = PAYLOAD_LEN;
			check_recv_pkts(rxfd, correct_payload, 2);
		} else if (proto == PF_INET6) {
			/* GRO doesn't check for ipv6 hop limit when flushing.
			 * Hence no corresponding test to the ipv4 case.
			 */
			printf("fragmented ip6 doesn't coalesce: ");
			correct_payload[0] = PAYLOAD_LEN * 2;
			correct_payload[1] = PAYLOAD_LEN;
			correct_payload[2] = PAYLOAD_LEN;
			check_recv_pkts(rxfd, correct_payload, 3);

			printf("ipv6 with ext header does coalesce: ");
			correct_payload[0] = PAYLOAD_LEN * 2;
			check_recv_pkts(rxfd, correct_payload, 1);

			printf("ipv6 with ext header with different payloads doesn't coalesce: ");
			correct_payload[0] = PAYLOAD_LEN;
			correct_payload[1] = PAYLOAD_LEN;
			check_recv_pkts(rxfd, correct_payload, 2);
		}
	} else if (strcmp(testname, "large") == 0) {
		int offset = proto == PF_INET ? 20 : 0;
		int remainder = (MAX_PAYLOAD + offset) % MSS;

		correct_payload[0] = (MAX_PAYLOAD + offset);
		correct_payload[1] = remainder;
		printf("Shouldn't coalesce if exceed IP max pkt size: ");
		check_recv_pkts(rxfd, correct_payload, 2);

		/* last segment sent individually, doesn't start new segment */
		correct_payload[0] = correct_payload[0] - remainder;
		correct_payload[1] = remainder + 1;
		correct_payload[2] = remainder + 1;
		check_recv_pkts(rxfd, correct_payload, 3);
	} else {
		error(1, 0, "Test case error, should never trigger");
	}

	if (close(rxfd))
		error(1, 0, "socket close");
}

static void parse_args(int argc, char **argv)
{
	static const struct option opts[] = {
		{ "daddr", required_argument, NULL, 'd' },
		{ "dmac", required_argument, NULL, 'D' },
		{ "iface", required_argument, NULL, 'i' },
		{ "ipv4", no_argument, NULL, '4' },
		{ "ipv6", no_argument, NULL, '6' },
		{ "rx", no_argument, NULL, 'r' },
		{ "saddr", required_argument, NULL, 's' },
		{ "smac", required_argument, NULL, 'S' },
		{ "test", required_argument, NULL, 't' },
		{ "verbose", no_argument, NULL, 'v' },
		{ 0, 0, 0, 0 }
	};
	int c;

	while ((c = getopt_long(argc, argv, "46d:D:i:rs:S:t:v", opts, NULL)) != -1) {
		switch (c) {
		case '4':
			proto = PF_INET;
			ethhdr_proto = htons(ETH_P_IP);
			break;
		case '6':
			proto = PF_INET6;
			ethhdr_proto = htons(ETH_P_IPV6);
			break;
		case 'd':
			addr4_dst = addr6_dst = optarg;
			break;
		case 'D':
			dmac = optarg;
			break;
		case 'i':
			ifname = optarg;
			break;
		case 'r':
			tx_socket = false;
			break;
		case 's':
			addr4_src = addr6_src = optarg;
			break;
		case 'S':
			smac = optarg;
			break;
		case 't':
			testname = optarg;
			break;
		case 'v':
			verbose = true;
			break;
		default:
			error(1, 0, "%s invalid option %c\n", __func__, c);
			break;
		}
	}
}

int main(int argc, char **argv)
{
	parse_args(argc, argv);

	if (proto == PF_INET) {
		tcp_offset = ETH_HLEN + sizeof(struct iphdr);
		total_hdr_len = tcp_offset + sizeof(struct tcphdr);
	} else if (proto == PF_INET6) {
		tcp_offset = ETH_HLEN + sizeof(struct ipv6hdr);
		total_hdr_len = MAX_HDR_LEN;
	} else {
		error(1, 0, "Protocol family is not ipv4 or ipv6");
	}

	read_MAC(src_mac, smac);
	read_MAC(dst_mac, dmac);

	if (tx_socket) {
		gro_sender();
	} else {
		/* Only the receiver exit status determines test success. */
		gro_receiver();
		fprintf(stderr, "Gro::%s test passed.\n", testname);
	}

	return 0;
}