On 7/31/24 12:31 PM, Kui-Feng Lee wrote:
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.)
IPv4 TCP packet: 127.0.0.1:48165 -> 127.0.0.1:36707, len 68, ifindex 1, SYN
IPv4 TCP packet: 127.0.0.1:36707 -> 127.0.0.1:48165, len 60, ifindex 1, SYN, ACK
IPv4 TCP packet: 127.0.0.1:48165 -> 127.0.0.1:36707, len 60, ifindex 1, ACK
IPv4 TCP packet: 127.0.0.1:36707 -> 127.0.0.1:48165, len 52, ifindex 1, ACK
IPv4 TCP packet: 127.0.0.1:48165 -> 127.0.0.1:36707, len 52, ifindex 1, FIN, ACK
IPv4 TCP packet: 127.0.0.1:36707 -> 127.0.0.1:48165, len 52, ifindex 1, RST, ACK
nit. Instead of ifindex, it should be ifname now.
Packet file: packets-2172-86-select_reuseport:sockhash-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 TRAFFIC_MONITOR variable has been passed to
build BPF selftests. For example,
make TRAFFIC_MONITOR=1 -C tools/testing/selftests/bpf
This command will build BPF selftests with this feature enabled.
Signed-off-by: Kui-Feng Lee <thinker.li@xxxxxxxxx>
---
tools/testing/selftests/bpf/Makefile | 5 +
tools/testing/selftests/bpf/test_progs.c | 432 +++++++++++++++++++++++
In the cover letter, it mentioned the traffic monitoring implementation is moved
from the network_helpers.c to test_progs.c.
Can you share more about the reason?
Is it because the traffic monitor now depends on the test_progs's test name,
should_tmon...etc ? Can the test name and should_tmon be exported for the
network_helpers to use?
What other compilation issues did it hit if the traffic monitor codes stay in
the network_helpers.c? Some individual binaries (with main()) like
test_tcp_check_syncookie_user that links to network_helpers.o but not to
test_progs.o?
+#ifdef TRAFFIC_MONITOR
+struct tmonitor_ctx {
+ pcap_t *pcap;
+ pcap_dumper_t *dumper;
+ pthread_t thread;
+ int wake_fd_r;
+ int wake_fd_w;
+
+ 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 */
+ return false;
+ }
+ return true;
+}
+
+/* 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)
+{
+ struct udphdr *udp;
+ struct tcphdr *tcp;
+ u16 src_port, dst_port;
+ const char *transport_str;
+ char *ifname, _ifname[IF_NAMESIZE];
+
+ 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("IPv4 ICMP packet: %s -> %s, len %d, type %d, code %d, ifname %s\n",
+ src_addr, dst_addr, len, packet[0], packet[1], ifname);
+ return;
+ } else if (proto == IPPROTO_ICMPV6) {
+ printf("IPv6 ICMPv6 packet: %s -> %s, len %d, type %d, code %d, ifname %s\n",
+ src_addr, dst_addr, len, packet[0], packet[1], ifname);
+ return;
+ } else {
+ printf("%s (proto %d): %s -> %s, ifname %s\n",
+ ipv6 ? "IPv6" : "IPv4", proto, src_addr, dst_addr, ifname);
+ return;
+ }
+
+ /* TCP */
+
+ if (ipv6)
+ printf("IPv6 %s packet: [%s]:%d -> [%s]:%d, len %d, ifname %s",
+ transport_str, src_addr, src_port,
+ dst_addr, dst_port, len, ifname);
+ else
+ printf("IPv4 %s packet: %s:%d -> %s:%d, len %d, ifname %s",
+ transport_str, src_addr, src_port,
+ dst_addr, dst_port, len, ifname);
+
+ 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");
The TCP packet output is done by multiple printf. There is a good chance that
one TCP packet is interleaved with the other printf(s), considering the traffic
monitoring is done in its own thread. I am seeing this in the tc_redirect test.
Does it help to do multiple snprintf (for the tcp flags?) first and then calls
one printf?
+}
+
+static void show_ipv6_packet(const u_char *packet, u32 ifindex)
+{
+ struct ipv6hdr *pkt = (struct ipv6hdr *)packet;
+ struct in6_addr src;
+ struct in6_addr dst;
+ char src_str[INET6_ADDRSTRLEN], dst_str[INET6_ADDRSTRLEN];
+ u_char proto;
+
+ memcpy(&src, &pkt->saddr, sizeof(src));
+ memcpy(&dst, &pkt->daddr, sizeof(dst));
+ inet_ntop(AF_INET6, &src, src_str, sizeof(src_str));
+ inet_ntop(AF_INET6, &dst, dst_str, sizeof(dst_str));
+ proto = pkt->nexthdr;
+ show_transport(packet + sizeof(struct ipv6hdr),
+ ntohs(pkt->payload_len),
+ ifindex, src_str, dst_str, proto, true);
+}
+
+static void show_ipv4_packet(const u_char *packet, u32 ifindex)
+{
+ struct iphdr *pkt = (struct iphdr *)packet;
+ struct in_addr src;
+ struct in_addr dst;
+ u_char proto;
+ char src_str[INET_ADDRSTRLEN], dst_str[INET_ADDRSTRLEN];
+
+ memcpy(&src, &pkt->saddr, sizeof(src));
+ memcpy(&dst, &pkt->daddr, sizeof(dst));
+ inet_ntop(AF_INET, &src, src_str, sizeof(src_str));
+ inet_ntop(AF_INET, &dst, dst_str, sizeof(dst_str));
+ proto = pkt->protocol;
+ show_transport(packet + sizeof(struct iphdr),
+ ntohs(pkt->tot_len),
+ ifindex, src_str, dst_str, proto, false);
+}
+
+static void *traffic_monitor_thread(void *arg)
+{
+ char *ifname, _ifname[IF_NAMESIZE];
+ const u_char *packet, *payload;
+ struct tmonitor_ctx *ctx = arg;
+ struct pcap_pkthdr header;
+ pcap_t *pcap = ctx->pcap;
+ pcap_dumper_t *dumper = ctx->dumper;
+ int fd = ctx->pcap_fd;
+ int wake_fd = ctx->wake_fd_r;
+ u16 proto;
+ u32 ifindex;
+ fd_set fds;
+ int nfds, r;
+
+ 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: %s", strerror(errno));
+ break;
+ }
+
+ 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);
The captured file has the "In", "Out", and "M" (Multicast) when it is read by
tcpdump. Is it easy to printf that in show_ipv[46]_packet() also? Just want to
ensure we didn't miss it if it is easy.
+
+ /* Not sure what other types of packets look like. Here, we
+ * parse only Ethernet and compatible packets.
+ */
+ if (!is_ethernet(packet)) {
+ printf("Packet captured\n");
+ 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);
+
+ if (proto == ETH_P_IPV6) {
+ show_ipv6_packet(payload, ifindex);
+ } else if (proto == ETH_P_IP) {
+ show_ipv4_packet(payload, ifindex);
+ } else {
+ ifname = if_indextoname(ifindex, _ifname);
+ if (!ifname) {
+ snprintf(_ifname, sizeof(_ifname), "unknown(%d)", ifindex);
+ ifname = _ifname;
+ }
+
+ printf("Unknown network protocol type %x, ifname %s\n", proto, ifname);
+ }
+ }
+
+ return NULL;
+}
