/* * Copyright (c) 2008 Damien Miller * * Permission to use, copy, modify, and distribute this software for any * purpose with or without fee is hereby granted, provided that the above * copyright notice and this permission notice appear in all copies. * * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #define DEFAULT_PORT "12345" #define DEFAULT_STATS_INTERVAL 1000 /* ms */ #define DEFAULT_BUF 256 * 1024 sig_atomic_t done = 0; sig_atomic_t print_stats = 0; struct statctx { struct timeval t_start, t_last, t_cur; unsigned long long bytes; pid_t pid; u_long tcbaddr; kvm_t *kh; char **kvars; }; /* When adding variables, also add to stats_display() */ static const char *allowed_kvars[] = { "inpcb.inp_flags", "sockb.so_rcv.sb_cc", "sockb.so_rcv.sb_hiwat", "sockb.so_snd.sb_cc", "sockb.so_snd.sb_hiwat", "tcpcb.snd_una", "tcpcb.snd_nxt", "tcpcb.snd_wl1", "tcpcb.snd_wl2", "tcpcb.snd_wnd", "tcpcb.rcv_wnd", "tcpcb.rcv_nxt", "tcpcb.rcv_adv", "tcpcb.snd_max", "tcpcb.snd_cwnd", "tcpcb.snd_ssthresh", "tcpcb.t_rcvtime", "tcpcb.t_rtttime", "tcpcb.t_rtseq", "tcpcb.t_srtt", "tcpcb.t_rttvar", "tcpcb.t_rttmin", "tcpcb.max_sndwnd", "tcpcb.snd_scale", "tcpcb.rcv_scale", "tcpcb.last_ack_sent", NULL }; static void exitsighand(int signo) { done = signo; } static void alarmhandler(int signo) { print_stats = 1; signal(signo, alarmhandler); } static void __dead usage(void) { fprintf(stderr, "usage: tcpbench -l\n" " tcpbench [-v] [-B buf] [-k kvars] [-n connections]" " [-p port] [-r rate]\n" " [-S space] hostname\n" " tcpbench -s [-v] [-B buf] [-k kvars] [-p port] [-r rate]" " [-S space]\n"); exit(1); } static void saddr_ntop(const struct sockaddr *addr, socklen_t alen, char *buf, size_t len) { char hbuf[NI_MAXHOST], pbuf[NI_MAXSERV]; int herr; if ((herr = getnameinfo(addr, alen, hbuf, sizeof(hbuf), pbuf, sizeof(pbuf), NI_NUMERICHOST|NI_NUMERICSERV)) != 0) { if (herr == EAI_SYSTEM) err(1, "getnameinfo"); else errx(1, "getnameinfo: %s", gai_strerror(herr)); } snprintf(buf, len, "[%s]:%s", hbuf, pbuf); } static void kget(kvm_t *kh, u_long addr, void *buf, int size) { if (kvm_read(kh, addr, buf, size) != size) errx(1, "kvm_read: %s", kvm_geterr(kh)); } static u_long kfind_tcb(kvm_t *kh, u_long ktcbtab, int sock, int vflag) { struct inpcbtable tcbtab; struct inpcb *head, *next, *prev; struct inpcb inpcb; struct tcpcb tcpcb; struct sockaddr_storage me, them; socklen_t melen, themlen; struct sockaddr_in *in4; struct sockaddr_in6 *in6; char tmp1[64], tmp2[64]; melen = themlen = sizeof(struct sockaddr_storage); if (getsockname(sock, (struct sockaddr *)&me, &melen) == -1) err(1, "getsockname"); if (getpeername(sock, (struct sockaddr *)&them, &themlen) == -1) err(1, "getpeername"); if (me.ss_family != them.ss_family) errx(1, "%s: me.ss_family != them.ss_family", __func__); if (me.ss_family != AF_INET && me.ss_family != AF_INET6) errx(1, "%s: unknown socket family", __func__); if (vflag >= 2) { saddr_ntop((struct sockaddr *)&me, me.ss_len, tmp1, sizeof(tmp1)); saddr_ntop((struct sockaddr *)&them, them.ss_len, tmp2, sizeof(tmp2)); fprintf(stderr, "Our socket local %s remote %s\n", tmp1, tmp2); } if (vflag >= 2) fprintf(stderr, "Using PCB table at %lu\n", ktcbtab); kget(kh, ktcbtab, &tcbtab, sizeof(tcbtab)); prev = head = (struct inpcb *)&CIRCLEQ_FIRST( &((struct inpcbtable *)ktcbtab)->inpt_queue); next = CIRCLEQ_FIRST(&tcbtab.inpt_queue); if (vflag >= 2) fprintf(stderr, "PCB head at %p\n", head); while (next != head) { if (vflag >= 2) fprintf(stderr, "Checking PCB %p\n", next); kget(kh, (u_long)next, &inpcb, sizeof(inpcb)); if (CIRCLEQ_PREV(&inpcb, inp_queue) != prev) errx(1, "pcb prev pointer insane"); prev = next; next = CIRCLEQ_NEXT(&inpcb, inp_queue); if (me.ss_family == AF_INET) { if ((inpcb.inp_flags & INP_IPV6) != 0) { if (vflag >= 2) fprintf(stderr, "Skip: INP_IPV6"); continue; } if (vflag >= 2) { inet_ntop(AF_INET, &inpcb.inp_laddr, tmp1, sizeof(tmp1)); inet_ntop(AF_INET, &inpcb.inp_faddr, tmp2, sizeof(tmp2)); fprintf(stderr, "PCB %p local: [%s]:%d " "remote: [%s]:%d\n", prev, tmp1, inpcb.inp_lport, tmp2, inpcb.inp_fport); } in4 = (struct sockaddr_in *)&me; if (memcmp(&in4->sin_addr, &inpcb.inp_laddr, sizeof(struct in_addr)) != 0 || in4->sin_port != inpcb.inp_lport) continue; in4 = (struct sockaddr_in *)&them; if (memcmp(&in4->sin_addr, &inpcb.inp_faddr, sizeof(struct in_addr)) != 0 || in4->sin_port != inpcb.inp_fport) continue; } else { if ((inpcb.inp_flags & INP_IPV6) == 0) continue; if (vflag >= 2) { inet_ntop(AF_INET6, &inpcb.inp_laddr6, tmp1, sizeof(tmp1)); inet_ntop(AF_INET6, &inpcb.inp_faddr6, tmp2, sizeof(tmp2)); fprintf(stderr, "PCB %p local: [%s]:%d " "remote: [%s]:%d\n", prev, tmp1, inpcb.inp_lport, tmp2, inpcb.inp_fport); } in6 = (struct sockaddr_in6 *)&me; if (memcmp(&in6->sin6_addr, &inpcb.inp_laddr6, sizeof(struct in6_addr)) != 0 || in6->sin6_port != inpcb.inp_lport) continue; in6 = (struct sockaddr_in6 *)&them; if (memcmp(&in6->sin6_addr, &inpcb.inp_faddr6, sizeof(struct in6_addr)) != 0 || in6->sin6_port != inpcb.inp_fport) continue; } kget(kh, (u_long)inpcb.inp_ppcb, &tcpcb, sizeof(tcpcb)); if (tcpcb.t_state != TCPS_ESTABLISHED) { if (vflag >= 2) fprintf(stderr, "Not established\n"); continue; } if (vflag >= 2) fprintf(stderr, "Found PCB at %p\n", prev); return (u_long)prev; } errx(1, "No matching PCB found"); } static void kupdate_stats(kvm_t *kh, u_long tcbaddr, struct inpcb *inpcb, struct tcpcb *tcpcb, struct socket *sockb) { kget(kh, tcbaddr, inpcb, sizeof(*inpcb)); kget(kh, (u_long)inpcb->inp_ppcb, tcpcb, sizeof(*tcpcb)); kget(kh, (u_long)inpcb->inp_socket, sockb, sizeof(*sockb)); } static void check_kvar(const char *var) { size_t i; for (i = 0; allowed_kvars[i] != NULL; i++) if (strcmp(allowed_kvars[i], var) == 0) return; errx(1, "Unrecognised kvar: %s", var); } static void list_kvars(void) { size_t i; fprintf(stderr, "Supported kernel variables:\n"); for (i = 0; allowed_kvars[i] != NULL; i++) fprintf(stderr, "\t%s\n", allowed_kvars[i]); } static char ** check_prepare_kvars(char *list) { char *item, **ret = NULL; size_t n = 0; while ((item = strsep(&list, ", \t\n")) != NULL) { check_kvar(item); if ((ret = realloc(ret, sizeof(*ret) * (++n + 1))) == NULL) errx(1, "realloc(kvars)"); if ((ret[n - 1] = strdup(item)) == NULL) errx(1, "strdup"); ret[n] = NULL; } return ret; } static void stats_prepare(struct statctx *sc, int fd, kvm_t *kh, u_long ktcbtab, int rflag, int vflag, char **kflag) { struct itimerval itv; int i; if (rflag <= 0) return; sc->kh = kh; sc->kvars = kflag; if (kflag) sc->tcbaddr = kfind_tcb(kh, ktcbtab, fd, vflag); gettimeofday(&sc->t_start, NULL); sc->t_last = sc->t_start; signal(SIGALRM, alarmhandler); itv.it_interval.tv_sec = rflag / 1000; itv.it_interval.tv_usec = (rflag % 1000) * 1000; itv.it_value = itv.it_interval; setitimer(ITIMER_REAL, &itv, NULL); sc->bytes = 0; sc->pid = getpid(); printf("%8s %12s %14s %12s ", "pid", "elapsed_ms", "bytes", "Mbps"); if (sc->kvars != NULL) { for (i = 0; sc->kvars[i] != NULL; i++) printf("%s%s", i > 0 ? "," : "", sc->kvars[i]); } printf("\n"); fflush(stdout); } static void stats_update(struct statctx *sc, ssize_t n) { sc->bytes += n; } static void stats_display(struct statctx *sc) { struct timeval t_diff; unsigned long long total_elapsed, since_last; size_t i; struct inpcb inpcb; struct tcpcb tcpcb; struct socket sockb; gettimeofday(&sc->t_cur, NULL); timersub(&sc->t_cur, &sc->t_start, &t_diff); total_elapsed = t_diff.tv_sec * 1000 + t_diff.tv_usec / 1000; timersub(&sc->t_cur, &sc->t_last, &t_diff); since_last = t_diff.tv_sec * 1000 + t_diff.tv_usec / 1000; printf("%8ld %12llu %14llu %12.3Lf ", (long)sc->pid, total_elapsed, sc->bytes, (long double)(sc->bytes * 8) / (since_last * 1000.0)); sc->t_last = sc->t_cur; sc->bytes = 0; if (sc->kvars != NULL) { kupdate_stats(sc->kh, sc->tcbaddr, &inpcb, &tcpcb, &sockb); for (i = 0; sc->kvars[i] != NULL; i++) { #define P(v, f) \ if (strcmp(sc->kvars[i], #v) == 0) { \ printf("%s"f, i > 0 ? "," : "", v); \ continue; \ } P(inpcb.inp_flags, "0x%08x") P(sockb.so_rcv.sb_cc, "%lu") P(sockb.so_rcv.sb_hiwat, "%lu") P(sockb.so_snd.sb_cc, "%lu") P(sockb.so_snd.sb_hiwat, "%lu") P(tcpcb.snd_una, "%u") P(tcpcb.snd_nxt, "%u") P(tcpcb.snd_wl1, "%u") P(tcpcb.snd_wl2, "%u") P(tcpcb.snd_wnd, "%lu") P(tcpcb.rcv_wnd, "%lu") P(tcpcb.rcv_nxt, "%u") P(tcpcb.rcv_adv, "%u") P(tcpcb.snd_max, "%u") P(tcpcb.snd_cwnd, "%lu") P(tcpcb.snd_ssthresh, "%lu") P(tcpcb.t_rcvtime, "%u") P(tcpcb.t_rtttime, "%u") P(tcpcb.t_rtseq, "%u") P(tcpcb.t_srtt, "%hu") P(tcpcb.t_rttvar, "%hu") P(tcpcb.t_rttmin, "%hu") P(tcpcb.max_sndwnd, "%lu") P(tcpcb.snd_scale, "%u") P(tcpcb.rcv_scale, "%u") P(tcpcb.last_ack_sent, "%u") #undef P } } printf("\n"); fflush(stdout); } static void stats_finish(struct statctx *sc) { struct itimerval itv; signal(SIGALRM, SIG_DFL); bzero(&itv, sizeof(itv)); setitimer(ITIMER_REAL, &itv, NULL); } static void __dead handle_connection(kvm_t *kvmh, u_long ktcbtab, int sock, int vflag, int rflag, char **kflag, int Bflag) { char *buf; struct pollfd pfd; ssize_t n; int r; struct statctx sc; if ((buf = malloc(Bflag)) == NULL) err(1, "malloc"); if ((r = fcntl(sock, F_GETFL, 0)) == -1) err(1, "fcntl(F_GETFL)"); r |= O_NONBLOCK; if (fcntl(sock, F_SETFL, r) == -1) err(1, "fcntl(F_SETFL, O_NONBLOCK)"); signal(SIGINT, exitsighand); signal(SIGTERM, exitsighand); signal(SIGHUP, exitsighand); signal(SIGPIPE, SIG_IGN); bzero(&pfd, sizeof(pfd)); pfd.fd = sock; pfd.events = POLLIN; stats_prepare(&sc, sock, kvmh, ktcbtab, rflag, vflag, kflag); while (!done) { if (print_stats) { stats_display(&sc); print_stats = 0; } if (poll(&pfd, 1, INFTIM) == -1) { if (errno == EINTR) continue; err(1, "poll"); } if ((n = read(pfd.fd, buf, Bflag)) == -1) { if (errno == EINTR || errno == EAGAIN) continue; err(1, "read"); } if (n == 0) { fprintf(stderr, "%8ld closed by remote end\n", (long)getpid()); done = -1; break; } if (vflag >= 3) fprintf(stderr, "read: %zd bytes\n", n); stats_update(&sc, n); } stats_finish(&sc); free(buf); close(sock); exit(1); } static void __dead serverloop(kvm_t *kvmh, u_long ktcbtab, struct addrinfo *aitop, int vflag, int rflag, char **kflag, int Sflag, int Bflag) { char tmp[128]; int r, sock, client_id, on = 1; struct addrinfo *ai; struct pollfd *pfd; struct sockaddr_storage ss; socklen_t sslen; size_t nfds, i, j; pfd = NULL; nfds = 0; for (ai = aitop; ai != NULL; ai = ai->ai_next) { saddr_ntop(ai->ai_addr, ai->ai_addrlen, tmp, sizeof(tmp)); if (vflag) fprintf(stderr, "Try listen on %s\n", tmp); if ((sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol)) == -1) { if (ai->ai_next == NULL) err(1, "socket"); if (vflag) warn("socket"); continue; } if (setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) == -1) warn("reuse port"); if (bind(sock, ai->ai_addr, ai->ai_addrlen) != 0) { if (ai->ai_next == NULL) err(1, "bind"); if (vflag) warn("bind"); close(sock); continue; } if (Sflag) { if (setsockopt(sock, SOL_SOCKET, SO_RCVBUF, &Sflag, sizeof(Sflag)) == -1) warn("set TCP receive buffer size"); } if (listen(sock, 64) == -1) { if (ai->ai_next == NULL) err(1, "listen"); if (vflag) warn("listen"); close(sock); continue; } if (nfds > 128) break; if ((pfd = realloc(pfd, ++nfds * sizeof(*pfd))) == NULL) errx(1, "realloc(pfd * %zu)", nfds); pfd[nfds - 1].fd = sock; pfd[nfds - 1].events = POLLIN; } freeaddrinfo(aitop); if (nfds == 0) errx(1, "No working listen addresses found"); signal(SIGINT, exitsighand); signal(SIGTERM, exitsighand); signal(SIGHUP, exitsighand); signal(SIGPIPE, SIG_IGN); signal(SIGCHLD, SIG_IGN); if (setpgid(0, 0) == -1) err(1, "setpgid"); client_id = 0; while (!done) { if ((r = poll(pfd, nfds, INFTIM)) == -1) { if (errno == EINTR) continue; warn("poll"); break; } if (vflag >= 3) fprintf(stderr, "poll: %d\n", r); for (i = 0 ; r > 0 && i < nfds; i++) { if ((pfd[i].revents & POLLIN) == 0) continue; if (vflag >= 3) fprintf(stderr, "fd %d active\n", pfd[i].fd); r--; sslen = sizeof(ss); if ((sock = accept(pfd[i].fd, (struct sockaddr *)&ss, &sslen)) == -1) { if (errno == EINTR) continue; warn("accept"); break; } saddr_ntop((struct sockaddr *)&ss, sslen, tmp, sizeof(tmp)); if (vflag) fprintf(stderr, "Accepted connection %d from " "%s, fd = %d\n", client_id++, tmp, sock); switch (fork()) { case -1: warn("fork"); done = -1; break; case 0: for (j = 0; j < nfds; j++) if (j != i) close(pfd[j].fd); handle_connection(kvmh, ktcbtab, sock, vflag, rflag, kflag, Bflag); /* NOTREACHED */ _exit(1); default: close(sock); break; } if (done == -1) break; } } for (i = 0; i < nfds; i++) close(pfd[i].fd); if (done > 0) warnx("Terminated by signal %d", done); signal(SIGTERM, SIG_IGN); killpg(0, SIGTERM); exit(1); } static void __dead clientloop(kvm_t *kvmh, u_long ktcbtab, const char *host, const char *port, int vflag, int rflag, char **kflag, int Sflag, int Bflag, int nconn) { char tmp[128]; char *buf; int r, sock, herr; struct addrinfo *aitop, *ai, hints; struct pollfd *pfd; ssize_t n; struct statctx sc; u_int i, scnt = 0; const char *errstr; if ((buf = malloc(Bflag)) == NULL) err(1, "malloc"); if ((pfd = calloc(nconn, sizeof(struct pollfd))) == NULL) err(1, "clientloop pfd calloc"); for (i = 0; i < nconn; i++) { bzero(&hints, sizeof(hints)); hints.ai_socktype = SOCK_STREAM; hints.ai_flags = 0; if ((herr = getaddrinfo(host, port, &hints, &aitop)) != 0) { if (herr == EAI_SYSTEM) err(1, "getaddrinfo"); else errx(1, "c getaddrinfo: %s", gai_strerror(herr)); } for (sock = -1, ai = aitop; ai != NULL; ai = ai->ai_next) { saddr_ntop(ai->ai_addr, ai->ai_addrlen, tmp, sizeof(tmp)); if (vflag && scnt == 0) fprintf(stderr, "Trying %s\n", tmp); if ((sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol)) == -1) { if (ai->ai_next == NULL) err(1, "socket"); if (vflag) warn("socket"); continue; } if (Sflag) { if (setsockopt(sock, SOL_SOCKET, SO_SNDBUF, &Sflag, sizeof(Sflag)) == -1) warn("set TCP send buffer size"); } if (connect(sock, ai->ai_addr, ai->ai_addrlen) != 0) { if (ai->ai_next == NULL) err(1, "connect"); if (vflag) warn("connect"); close(sock); sock = -1; continue; } break; } freeaddrinfo(aitop); if (sock == -1) errx(1, "No host found"); if ((r = fcntl(sock, F_GETFL, 0)) == -1) err(1, "fcntl(F_GETFL)"); r |= O_NONBLOCK; if (fcntl(sock, F_SETFL, r) == -1) err(1, "fcntl(F_SETFL, O_NONBLOCK)"); pfd[i].fd = sock; pfd[i].events = POLLOUT; scnt++; } if (vflag && scnt > 1) fprintf(stderr, "%u connections established\n", scnt); arc4random_buf(buf, Bflag); signal(SIGINT, exitsighand); signal(SIGTERM, exitsighand); signal(SIGHUP, exitsighand); signal(SIGPIPE, SIG_IGN); stats_prepare(&sc, sock, kvmh, ktcbtab, rflag, vflag, kflag); while (!done) { if (print_stats) { stats_display(&sc); print_stats = 0; } if (poll(pfd, nconn, INFTIM) == -1) { if (errno == EINTR) continue; err(1, "poll"); } for (i = 0; i < nconn; i++) { if (pfd[i].revents & POLLOUT) if ((n = write(pfd[i].fd, buf, Bflag)) == -1) { if (errno == EINTR || errno == EAGAIN) continue; err(1, "write"); } if (n == 0) { warnx("Remote end closed connection"); done = -1; break; } if (vflag >= 3) fprintf(stderr, "write: %zd bytes\n", n); stats_update(&sc, n); } } stats_finish(&sc); if (done > 0) warnx("Terminated by signal %d", done); free(buf); close(sock); exit(0); } static void drop_gid(void) { gid_t gid; gid = getgid(); if (setresgid(gid, gid, gid) == -1) err(1, "setresgid"); } int main(int argc, char **argv) { extern int optind; extern char *optarg; char kerr[_POSIX2_LINE_MAX], *tmp; const char *errstr; int ch, herr; struct addrinfo *aitop, hints; kvm_t *kvmh = NULL; const char *host = NULL, *port = DEFAULT_PORT; char **kflag = NULL; int sflag = 0, vflag = 0, rflag = DEFAULT_STATS_INTERVAL, Sflag = 0; int Bflag = DEFAULT_BUF; int nconn = 1; struct nlist nl[] = { { "_tcbtable" }, { "" } }; while ((ch = getopt(argc, argv, "B:hlk:n:p:r:sS:v")) != -1) { switch (ch) { case 'l': list_kvars(); exit(0); case 'k': if ((tmp = strdup(optarg)) == NULL) errx(1, "strdup"); kflag = check_prepare_kvars(tmp); free(tmp); break; case 'r': rflag = strtonum(optarg, 0, 60 * 60 * 24 * 1000, &errstr); if (errstr != NULL) errx(1, "statistics interval is %s: %s", errstr, optarg); break; case 'p': port = optarg; break; case 's': sflag = 1; break; case 'S': Sflag = strtonum(optarg, 0, 1024*1024*1024, &errstr); if (errstr != NULL) errx(1, "receive space interval is %s: %s", errstr, optarg); break; case 'B': Bflag = strtonum(optarg, 0, 1024*1024*1024, &errstr); if (errstr != NULL) errx(1, "read/write buffer size is %s: %s", errstr, optarg); break; case 'v': if (vflag < 2) vflag++; break; case 'n': nconn = strtonum(optarg, 0, 65535, &errstr); if (errstr != NULL) errx(1, "number of connections is %s: %s", errstr, optarg); break; case 'h': default: usage(); } } argv += optind; argc -= optind; if (argc != (sflag ? 0 : 1)) usage(); if (kflag != NULL && nconn > 1) errx(1, "-k currently only works with a single tcp connection"); if (!sflag) host = argv[0]; if (sflag) { bzero(&hints, sizeof(hints)); hints.ai_socktype = SOCK_STREAM; hints.ai_flags = AI_PASSIVE; if ((herr = getaddrinfo(host, port, &hints, &aitop)) != 0) { if (herr == EAI_SYSTEM) err(1, "getaddrinfo"); else errx(1, "s getaddrinfo: %s", gai_strerror(herr)); } } if (kflag) { if ((kvmh = kvm_openfiles(NULL, NULL, NULL, O_RDONLY, kerr)) == NULL) errx(1, "kvm_open: %s", kerr); drop_gid(); if (kvm_nlist(kvmh, nl) < 0 || nl[0].n_type == 0) errx(1, "kvm: no namelist"); } else drop_gid(); if (sflag) serverloop(kvmh, nl[0].n_value, aitop, vflag, rflag, kflag, Sflag, Bflag); else clientloop(kvmh, nl[0].n_value, host, port, vflag, rflag, kflag, Sflag, Bflag, nconn); return 0; }