text: // SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
  // Copyright (c) 2021 Hengqi Chen
  //
  // Based on gethostlatency(8) from BCC by Brendan Gregg.
  // 24-Mar-2021   Hengqi Chen   Created this.
  #include <argp.h>
  #include <errno.h>
  #include <signal.h>
  #include <time.h>
  
  #include <bpf/libbpf.h>
  #include <bpf/bpf.h>
  #include "gethostlatency.h"
  #include "gethostlatency.skel.h"
  #include "trace_helpers.h"
  #include "uprobe_helpers.h"
  
  #define PERF_BUFFER_PAGES 16
  #define PERF_POLL_TIMEOUT_MS 100
  #define warn(...) fprintf(stderr, __VA_ARGS__)
  
  static volatile sig_atomic_t exiting = 0;
  static pid_t traced_pid = 0;
  
  const char *argp_program_version = "gethostlatency 0.1";
  const char *argp_program_bug_address =
  	"https://github.com/iovisor/bcc/tree/master/libbpf-tools";
  const char argp_program_doc[] =
  "Show latency for getaddrinfo/gethostbyname[2] calls.\n"
  "\n"
  "USAGE: gethostlatency [-h] [-p PID]\n"
  "\n"
  "EXAMPLES:\n"
  "    gethostlatency             # time getaddrinfo/gethostbyname[2] calls\n"
  "    gethostlatency -p 1216     # only trace PID 1216\n";
  
  static const struct argp_option opts[] = {
  	{ "pid", 'p', "PID", 0, "Process ID to trace" },
  	{ NULL, 'h', NULL, OPTION_HIDDEN, "Show the full help" },
  	{},
  };
  
  static error_t parse_arg(int key, char *arg, struct argp_state *state)
  {
  	long pid;
  
  	switch (key) {
  	case 'p':
  		errno = 0;
  		pid = strtol(arg, NULL, 10);
  		if (errno || pid <= 0) {
  			warn("Invalid PID: %s\n", arg);
  			argp_usage(state);
  		}
  		traced_pid = pid;
  		break;
  	case 'h':
  		argp_state_help(state, stderr, ARGP_HELP_STD_HELP);
  		break;
  	default:
  		return ARGP_ERR_UNKNOWN;
  	}
  	return 0;
  }
  
  static void sig_int(int signo)
  {
  	exiting = 1;
  }
  
  static const char *strftime_now(char *s, size_t max, const char *format)
  {
  	struct tm *tm;
  	time_t t;
  
  	t = time(NULL);
  	tm = localtime(&t);
  	if (tm == NULL) {
  		warn("localtime: %s\n", strerror(errno));
  		return "<failed>";
  	}
  	if (strftime(s, max, format, tm) == 0) {
  		warn("strftime error\n");
  		return "<failed>";
  	}
  	return s;
  }
  
  static void handle_event(void *ctx, int cpu, void *data, __u32 data_sz)
  {
  	const struct val_t *e = data;
  	char s[16] = {};
  	const char *now;
  
  	now = strftime_now(s, sizeof(s), "%H:%M:%S");
  	printf("%-11s %-10d %-20s %-10.2f %-16s\n",
  		now, e->pid, e->comm, (double)e->time/1000000, e->host);
  }
  
  static void handle_lost_events(void *ctx, int cpu, __u64 lost_cnt)
  {
  	warn("lost %llu events on CPU #%d\n", lost_cnt, cpu);
  }
  
  static int get_libc_path(char *path)
  {
  	FILE *f;
  	char buf[256] = {};
  	char *filename;
  	float version;
  
  	f = fopen("/proc/self/maps", "r");
  	if (!f) {
  		return -errno;
  	}
  
  	while (fscanf(f, "%*x-%*x %*s %*s %*s %*s %[^\n]\n", buf) != EOF) {
  		if (strchr(buf, '/') != buf) {
  			continue;
  		}
  		filename = strrchr(buf, '/') + 1;
  		if (sscanf(filename, "libc-%f.so", &version) == 1) {
  			memcpy(path, buf, strlen(buf));
  			fclose(f);
  			return 0;
  		}
  	}
  
  	fclose(f);
  	return -1;
  }
  
  static int attach_uprobes(struct gethostlatency_bpf *obj)
  {
  	int err;
  	char libc_path[PATH_MAX] = {};
  	off_t func_off;
  
  	err = get_libc_path(libc_path);
  	if (err) {
  		warn("could not find libc.so\n");
  		return -1;
  	}
  
  	func_off = get_elf_func_offset(libc_path, "getaddrinfo");
  	if (func_off < 0) {
  		warn("could not find getaddrinfo in %s\n", libc_path);
  		return -1;
  	}
  	obj->links.handle_entry =
  		bpf_program__attach_uprobe(obj->progs.handle_entry, false,
  					   traced_pid ?: -1, libc_path, func_off);
  	err = libbpf_get_error(obj->links.handle_entry);
  	if (err) {
  		warn("failed to attach getaddrinfo: %d\n", err);
  		return -1;
  	}
  	obj->links.handle_return =
  		bpf_program__attach_uprobe(obj->progs.handle_return, true,
  					   traced_pid ?: -1, libc_path, func_off);
  	err = libbpf_get_error(obj->links.handle_return);
  	if (err) {
  		warn("failed to attach getaddrinfo: %d\n", err);
  		return -1;
  	}
  
  	func_off = get_elf_func_offset(libc_path, "gethostbyname");
  	if (func_off < 0) {
  		warn("Could not find gethostbyname in %s\n", libc_path);
  		return -1;
  	}
  	obj->links.handle_entry =
  		bpf_program__attach_uprobe(obj->progs.handle_entry, false,
  					   traced_pid ?: -1, libc_path, func_off);
  	err = libbpf_get_error(obj->links.handle_entry);
  	if (err) {
  		warn("failed to attach gethostbyname: %d\n", err);
  		return -1;
  	}
  	obj->links.handle_return =
  		bpf_program__attach_uprobe(obj->progs.handle_return, true,
  					   traced_pid ?: -1, libc_path, func_off);
  	err = libbpf_get_error(obj->links.handle_return);
  	if (err) {
  		warn("failed to attach gethostbyname: %d\n", err);
  		return -1;
  	}
  
  	func_off = get_elf_func_offset(libc_path, "gethostbyname2");
  	if (func_off < 0) {
  		warn("Could not find gethostbyname2 in %s\n", libc_path);
  		return -1;
  	}
  	obj->links.handle_entry =
  		bpf_program__attach_uprobe(obj->progs.handle_entry, false,
  					   traced_pid ?: -1, libc_path, func_off);
  	err = libbpf_get_error(obj->links.handle_entry);
  	if (err) {
  		warn("failed to attach gethostbyname2: %d\n", err);
  		return -1;
  	}
  	obj->links.handle_return =
  		bpf_program__attach_uprobe(obj->progs.handle_return, true,
  					   traced_pid ?: -1, libc_path, func_off);
  	err = libbpf_get_error(obj->links.handle_return);
  	if (err) {
  		warn("failed to attach gethostbyname2: %d\n", err);
  		return -1;
  	}
  
  	return 0;
  }
  
  int main(int argc, char **argv)
  {
  	static const struct argp argp = {
  		.options = opts,
  		.parser = parse_arg,
  		.doc = argp_program_doc,
  	};
  	struct perf_buffer_opts pb_opts;
  	struct perf_buffer *pb = NULL;
  	struct gethostlatency_bpf *obj;
  	int err;
  
  	err = argp_parse(&argp, argc, argv, 0, NULL, NULL);
  	if (err)
  		return err;
  
  	err = bump_memlock_rlimit();
  	if (err) {
  		warn("failed to increase rlimit: %d\n", err);
  		return 1;
  	}
  
  	obj = gethostlatency_bpf__open();
  	if (!obj) {
  		warn("failed to open BPF object\n");
  		return 1;
  	}
  
  	obj->rodata->targ_tgid = traced_pid;
  
  	err = gethostlatency_bpf__load(obj);
  	if (err) {
  		warn("failed to load BPF object: %d\n", err);
  		goto cleanup;
  	}
  
  	err = attach_uprobes(obj);
  	if (err) {
  		goto cleanup;
  	}
  
  	pb_opts.sample_cb = handle_event;
  	pb_opts.lost_cb = handle_lost_events;
  	pb = perf_buffer__new(bpf_map__fd(obj->maps.events), PERF_BUFFER_PAGES,
  			&pb_opts);
  	err = libbpf_get_error(pb);
  	if (err) {
  		warn("failed to open perf buffer: %d\n", err);
  		goto cleanup;
  	}
  
  	if (signal(SIGINT, sig_int) == SIG_ERR) {
  		warn("can't set signal handler: %s\n", strerror(-errno));
  		goto cleanup;
  	}
  
  	printf("%-11s %-10s %-20s %-10s %-16s\n",
  		"TIME", "PID", "COMM", "LATms", "HOST");
  
  	while (1) {
  		if ((err = perf_buffer__poll(pb, PERF_POLL_TIMEOUT_MS)) < 0)
  			break;
  		if (exiting)
  			goto cleanup;
  	}
  	warn("error polling perf buffer: %d\n", err);
  
  cleanup:
  	gethostlatency_bpf__destroy(obj);
  
  	return err != 0;
  }
  