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selftests/bpf: Add traffic monitor functions.

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Add functions that capture packets and print log in the background. They
are supposed to be used for debugging flaky network test cases. A monitored
test case should call traffic_monitor_start() to start a thread to capture
packets in the background for a given namespace and call
traffic_monitor_stop() to stop capturing. (Or, option '-m' implemented by
the later patches.)

    lo      In  IPv4 127.0.0.1:40265 > 127.0.0.1:55907: TCP, length 68, SYN
    lo      In  IPv4 127.0.0.1:55907 > 127.0.0.1:40265: TCP, length 60, SYN, ACK
    lo      In  IPv4 127.0.0.1:40265 > 127.0.0.1:55907: TCP, length 60, ACK
    lo      In  IPv4 127.0.0.1:55907 > 127.0.0.1:40265: TCP, length 52, ACK
    lo      In  IPv4 127.0.0.1:40265 > 127.0.0.1:55907: TCP, length 52, FIN, ACK
    lo      In  IPv4 127.0.0.1:55907 > 127.0.0.1:40265: TCP, length 52, RST, ACK
    Packet file: packets-2173-86-select_reuseport:sockhash_IPv4_TCP_LOOPBACK_test_detach_bpf-test.log
    #280/87 select_reuseport/sockhash IPv4/TCP LOOPBACK test_detach_bpf:OK

The above is the output of an example. It shows the packets of a connection
and the name of the file that contains captured packets in the directory
/tmp/tmon_pcap. The file can be loaded by tcpdump or wireshark.

This feature only works if libpcap is available. (Could be found by pkg-config)

Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Signed-off-by: Kui-Feng Lee <thinker.li@gmail.com>
Link: https://lore.kernel.org/r/20240815053254.470944-2-thinker.li@gmail.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
This commit is contained in:
Kui-Feng Lee 2024-08-14 22:32:49 -07:00 committed by Martin KaFai Lau
parent b97ce54743
commit f52403b6bf
3 changed files with 476 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
tools/testing/selftests/bpf/Makefile
View File

@ -41,6 +41,10 @@ CFLAGS += -g $(OPT_FLAGS) -rdynamic \
LDFLAGS += $(SAN_LDFLAGS)
LDLIBS += $(LIBELF_LIBS) -lz -lrt -lpthread
LDLIBS += $(shell $(PKG_CONFIG) --libs libpcap 2>/dev/null)
CFLAGS += $(shell $(PKG_CONFIG) --cflags libpcap 2>/dev/null)
CFLAGS += $(shell $(PKG_CONFIG) --exists libpcap 2>/dev/null && echo "-DTRAFFIC_MONITOR=1")
# The following tests perform type punning and they may break strict
# aliasing rules, which are exploited by both GCC and clang by default
# while optimizing. This can lead to broken programs.

454
tools/testing/selftests/bpf/network_helpers.c
View File

@ -11,17 +11,31 @@
#include <arpa/inet.h>
#include <sys/mount.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/un.h>
#include <sys/eventfd.h>
#include <linux/err.h>
#include <linux/in.h>
#include <linux/in6.h>
#include <linux/limits.h>
#include <linux/ip.h>
#include <linux/udp.h>
#include <netinet/tcp.h>
#include <net/if.h>
#include "bpf_util.h"
#include "network_helpers.h"
#include "test_progs.h"
#ifdef TRAFFIC_MONITOR
/* Prevent pcap.h from including pcap/bpf.h and causing conflicts */
#define PCAP_DONT_INCLUDE_PCAP_BPF_H 1
#include <pcap/pcap.h>
#include <pcap/dlt.h>
#endif
#ifndef IPPROTO_MPTCP
#define IPPROTO_MPTCP 262
#endif
@ -660,3 +674,443 @@ int send_recv_data(int lfd, int fd, uint32_t total_bytes)
return err;
}
#ifdef TRAFFIC_MONITOR
struct tmonitor_ctx {
pcap_t *pcap;
pcap_dumper_t *dumper;
pthread_t thread;
int wake_fd;
volatile bool done;
char pkt_fname[PATH_MAX];
int pcap_fd;
};
/* Is this packet captured with a Ethernet protocol type? */
static bool is_ethernet(const u_char *packet)
{
u16 arphdr_type;
memcpy(&arphdr_type, packet + 8, 2);
arphdr_type = ntohs(arphdr_type);
/* Except the following cases, the protocol type contains the
* Ethernet protocol type for the packet.
*
* https://www.tcpdump.org/linktypes/LINKTYPE_LINUX_SLL2.html
*/
switch (arphdr_type) {
case 770: /* ARPHRD_FRAD */
case 778: /* ARPHDR_IPGRE */
case 803: /* ARPHRD_IEEE80211_RADIOTAP */
printf("Packet captured: arphdr_type=%d\n", arphdr_type);
return false;
}
return true;
}
static const char * const pkt_types[] = {
"In",
"B", /* Broadcast */
"M", /* Multicast */
"C", /* Captured with the promiscuous mode */
"Out",
};
static const char *pkt_type_str(u16 pkt_type)
{
if (pkt_type < ARRAY_SIZE(pkt_types))
return pkt_types[pkt_type];
return "Unknown";
}
/* Show the information of the transport layer in the packet */
static void show_transport(const u_char *packet, u16 len, u32 ifindex,
const char *src_addr, const char *dst_addr,
u16 proto, bool ipv6, u8 pkt_type)
{
char *ifname, _ifname[IF_NAMESIZE];
const char *transport_str;
u16 src_port, dst_port;
struct udphdr *udp;
struct tcphdr *tcp;
ifname = if_indextoname(ifindex, _ifname);
if (!ifname) {
snprintf(_ifname, sizeof(_ifname), "unknown(%d)", ifindex);
ifname = _ifname;
}
if (proto == IPPROTO_UDP) {
udp = (struct udphdr *)packet;
src_port = ntohs(udp->source);
dst_port = ntohs(udp->dest);
transport_str = "UDP";
} else if (proto == IPPROTO_TCP) {
tcp = (struct tcphdr *)packet;
src_port = ntohs(tcp->source);
dst_port = ntohs(tcp->dest);
transport_str = "TCP";
} else if (proto == IPPROTO_ICMP) {
printf("%-7s %-3s IPv4 %s > %s: ICMP, length %d, type %d, code %d\n",
ifname, pkt_type_str(pkt_type), src_addr, dst_addr, len,
packet[0], packet[1]);
return;
} else if (proto == IPPROTO_ICMPV6) {
printf("%-7s %-3s IPv6 %s > %s: ICMPv6, length %d, type %d, code %d\n",
ifname, pkt_type_str(pkt_type), src_addr, dst_addr, len,
packet[0], packet[1]);
return;
} else {
printf("%-7s %-3s %s %s > %s: protocol %d\n",
ifname, pkt_type_str(pkt_type), ipv6 ? "IPv6" : "IPv4",
src_addr, dst_addr, proto);
return;
}
/* TCP or UDP*/
flockfile(stdout);
if (ipv6)
printf("%-7s %-3s IPv6 %s.%d > %s.%d: %s, length %d",
ifname, pkt_type_str(pkt_type), src_addr, src_port,
dst_addr, dst_port, transport_str, len);
else
printf("%-7s %-3s IPv4 %s:%d > %s:%d: %s, length %d",
ifname, pkt_type_str(pkt_type), src_addr, src_port,
dst_addr, dst_port, transport_str, len);
if (proto == IPPROTO_TCP) {
if (tcp->fin)
printf(", FIN");
if (tcp->syn)
printf(", SYN");
if (tcp->rst)
printf(", RST");
if (tcp->ack)
printf(", ACK");
}
printf("\n");
funlockfile(stdout);
}
static void show_ipv6_packet(const u_char *packet, u32 ifindex, u8 pkt_type)
{
char src_buf[INET6_ADDRSTRLEN], dst_buf[INET6_ADDRSTRLEN];
struct ipv6hdr *pkt = (struct ipv6hdr *)packet;
const char *src, *dst;
u_char proto;
src = inet_ntop(AF_INET6, &pkt->saddr, src_buf, sizeof(src_buf));
if (!src)
src = "<invalid>";
dst = inet_ntop(AF_INET6, &pkt->daddr, dst_buf, sizeof(dst_buf));
if (!dst)
dst = "<invalid>";
proto = pkt->nexthdr;
show_transport(packet + sizeof(struct ipv6hdr),
ntohs(pkt->payload_len),
ifindex, src, dst, proto, true, pkt_type);
}
static void show_ipv4_packet(const u_char *packet, u32 ifindex, u8 pkt_type)
{
char src_buf[INET_ADDRSTRLEN], dst_buf[INET_ADDRSTRLEN];
struct iphdr *pkt = (struct iphdr *)packet;
const char *src, *dst;
u_char proto;
src = inet_ntop(AF_INET, &pkt->saddr, src_buf, sizeof(src_buf));
if (!src)
src = "<invalid>";
dst = inet_ntop(AF_INET, &pkt->daddr, dst_buf, sizeof(dst_buf));
if (!dst)
dst = "<invalid>";
proto = pkt->protocol;
show_transport(packet + sizeof(struct iphdr),
ntohs(pkt->tot_len),
ifindex, src, dst, proto, false, pkt_type);
}
static void *traffic_monitor_thread(void *arg)
{
char *ifname, _ifname[IF_NAMESIZE];
const u_char *packet, *payload;
struct tmonitor_ctx *ctx = arg;
pcap_dumper_t *dumper = ctx->dumper;
int fd = ctx->pcap_fd, nfds, r;
int wake_fd = ctx->wake_fd;
struct pcap_pkthdr header;
pcap_t *pcap = ctx->pcap;
u32 ifindex;
fd_set fds;
u16 proto;
u8 ptype;
nfds = (fd > wake_fd ? fd : wake_fd) + 1;
FD_ZERO(&fds);
while (!ctx->done) {
FD_SET(fd, &fds);
FD_SET(wake_fd, &fds);
r = select(nfds, &fds, NULL, NULL, NULL);
if (!r)
continue;
if (r < 0) {
if (errno == EINTR)
continue;
log_err("Fail to select on pcap fd and wake fd");
break;
}
/* This instance of pcap is non-blocking */
packet = pcap_next(pcap, &header);
if (!packet)
continue;
/* According to the man page of pcap_dump(), first argument
* is the pcap_dumper_t pointer even it's argument type is
* u_char *.
*/
pcap_dump((u_char *)dumper, &header, packet);
/* Not sure what other types of packets look like. Here, we
* parse only Ethernet and compatible packets.
*/
if (!is_ethernet(packet))
continue;
/* Skip SLL2 header
* https://www.tcpdump.org/linktypes/LINKTYPE_LINUX_SLL2.html
*
* Although the document doesn't mention that, the payload
* doesn't include the Ethernet header. The payload starts
* from the first byte of the network layer header.
*/
payload = packet + 20;
memcpy(&proto, packet, 2);
proto = ntohs(proto);
memcpy(&ifindex, packet + 4, 4);
ifindex = ntohl(ifindex);
ptype = packet[10];
if (proto == ETH_P_IPV6) {
show_ipv6_packet(payload, ifindex, ptype);
} else if (proto == ETH_P_IP) {
show_ipv4_packet(payload, ifindex, ptype);
} else {
ifname = if_indextoname(ifindex, _ifname);
if (!ifname) {
snprintf(_ifname, sizeof(_ifname), "unknown(%d)", ifindex);
ifname = _ifname;
}
printf("%-7s %-3s Unknown network protocol type 0x%x\n",
ifname, pkt_type_str(ptype), proto);
}
}
return NULL;
}
/* Prepare the pcap handle to capture packets.
*
* This pcap is non-blocking and immediate mode is enabled to receive
* captured packets as soon as possible. The snaplen is set to 1024 bytes
* to limit the size of captured content. The format of the link-layer
* header is set to DLT_LINUX_SLL2 to enable handling various link-layer
* technologies.
*/
static pcap_t *traffic_monitor_prepare_pcap(void)
{
char errbuf[PCAP_ERRBUF_SIZE];
pcap_t *pcap;
int r;
/* Listen on all NICs in the namespace */
pcap = pcap_create("any", errbuf);
if (!pcap) {
log_err("Failed to open pcap: %s", errbuf);
return NULL;
}
/* Limit the size of the packet (first N bytes) */
r = pcap_set_snaplen(pcap, 1024);
if (r) {
log_err("Failed to set snaplen: %s", pcap_geterr(pcap));
goto error;
}
/* To receive packets as fast as possible */
r = pcap_set_immediate_mode(pcap, 1);
if (r) {
log_err("Failed to set immediate mode: %s", pcap_geterr(pcap));
goto error;
}
r = pcap_setnonblock(pcap, 1, errbuf);
if (r) {
log_err("Failed to set nonblock: %s", errbuf);
goto error;
}
r = pcap_activate(pcap);
if (r) {
log_err("Failed to activate pcap: %s", pcap_geterr(pcap));
goto error;
}
/* Determine the format of the link-layer header */
r = pcap_set_datalink(pcap, DLT_LINUX_SLL2);
if (r) {
log_err("Failed to set datalink: %s", pcap_geterr(pcap));
goto error;
}
return pcap;
error:
pcap_close(pcap);
return NULL;
}
static void encode_test_name(char *buf, size_t len, const char *test_name, const char *subtest_name)
{
char *p;
if (subtest_name)
snprintf(buf, len, "%s__%s", test_name, subtest_name);
else
snprintf(buf, len, "%s", test_name);
while ((p = strchr(buf, '/')))
*p = '_';
while ((p = strchr(buf, ' ')))
*p = '_';
}
#define PCAP_DIR "/tmp/tmon_pcap"
/* Start to monitor the network traffic in the given network namespace.
*
* netns: the name of the network namespace to monitor. If NULL, the
* current network namespace is monitored.
* test_name: the name of the running test.
* subtest_name: the name of the running subtest if there is. It should be
* NULL if it is not a subtest.
*
* This function will start a thread to capture packets going through NICs
* in the give network namespace.
*/
struct tmonitor_ctx *traffic_monitor_start(const char *netns, const char *test_name,
const char *subtest_name)
{
struct nstoken *nstoken = NULL;
struct tmonitor_ctx *ctx;
char test_name_buf[64];
static int tmon_seq;
int r;
if (netns) {
nstoken = open_netns(netns);
if (!nstoken)
return NULL;
}
ctx = malloc(sizeof(*ctx));
if (!ctx) {
log_err("Failed to malloc ctx");
goto fail_ctx;
}
memset(ctx, 0, sizeof(*ctx));
encode_test_name(test_name_buf, sizeof(test_name_buf), test_name, subtest_name);
snprintf(ctx->pkt_fname, sizeof(ctx->pkt_fname),
PCAP_DIR "/packets-%d-%d-%s-%s.log", getpid(), tmon_seq++,
test_name_buf, netns ? netns : "unknown");
r = mkdir(PCAP_DIR, 0755);
if (r && errno != EEXIST) {
log_err("Failed to create " PCAP_DIR);
goto fail_pcap;
}
ctx->pcap = traffic_monitor_prepare_pcap();
if (!ctx->pcap)
goto fail_pcap;
ctx->pcap_fd = pcap_get_selectable_fd(ctx->pcap);
if (ctx->pcap_fd < 0) {
log_err("Failed to get pcap fd");
goto fail_dumper;
}
/* Create a packet file */
ctx->dumper = pcap_dump_open(ctx->pcap, ctx->pkt_fname);
if (!ctx->dumper) {
log_err("Failed to open pcap dump: %s", ctx->pkt_fname);
goto fail_dumper;
}
/* Create an eventfd to wake up the monitor thread */
ctx->wake_fd = eventfd(0, 0);
if (ctx->wake_fd < 0) {
log_err("Failed to create eventfd");
goto fail_eventfd;
}
r = pthread_create(&ctx->thread, NULL, traffic_monitor_thread, ctx);
if (r) {
log_err("Failed to create thread");
goto fail;
}
close_netns(nstoken);
return ctx;
fail:
close(ctx->wake_fd);
fail_eventfd:
pcap_dump_close(ctx->dumper);
unlink(ctx->pkt_fname);
fail_dumper:
pcap_close(ctx->pcap);
fail_pcap:
free(ctx);
fail_ctx:
close_netns(nstoken);
return NULL;
}
static void traffic_monitor_release(struct tmonitor_ctx *ctx)
{
pcap_close(ctx->pcap);
pcap_dump_close(ctx->dumper);
close(ctx->wake_fd);
free(ctx);
}
/* Stop the network traffic monitor.
*
* ctx: the context returned by traffic_monitor_start()
*/
void traffic_monitor_stop(struct tmonitor_ctx *ctx)
{
__u64 w = 1;
if (!ctx)
return;
/* Stop the monitor thread */
ctx->done = true;
/* Wake up the background thread. */
write(ctx->wake_fd, &w, sizeof(w));
pthread_join(ctx->thread, NULL);
printf("Packet file: %s\n", strrchr(ctx->pkt_fname, '/') + 1);
traffic_monitor_release(ctx);
}
#endif /* TRAFFIC_MONITOR */

18
tools/testing/selftests/bpf/network_helpers.h
View File

@ -136,4 +136,22 @@ static inline __sum16 csum_ipv6_magic(const struct in6_addr *saddr,
return csum_fold((__u32)s);
}
struct tmonitor_ctx;
#ifdef TRAFFIC_MONITOR
struct tmonitor_ctx *traffic_monitor_start(const char *netns, const char *test_name,
const char *subtest_name);
void traffic_monitor_stop(struct tmonitor_ctx *ctx);
#else
static inline struct tmonitor_ctx *traffic_monitor_start(const char *netns, const char *test_name,
const char *subtest_name)
{
return NULL;
}
static inline void traffic_monitor_stop(struct tmonitor_ctx *ctx)
{
}
#endif
#endif