ref: cbe4b116989c0bfec49b9ae7a1d9a85ead6648ae
dir: /sys/src/cmd/webfs/http.c/
#include <u.h> #include <libc.h> #include <ctype.h> #include <fcall.h> #include <thread.h> #include <9p.h> #include "dat.h" #include "fns.h" #include <auth.h> #include <mp.h> #include <libsec.h> typedef struct Hconn Hconn; typedef struct Hpool Hpool; typedef struct Hauth Hauth; struct Hconn { Hconn *next; long time; int fd; int ctl; int keep; int cancel; int tunnel; int len; char addr[128]; char buf[8192+2]; }; struct Hpool { QLock; Hconn *head; int active; int limit; int peer; int idle; }; struct Hauth { Hauth *next; Url *url; char *auth; }; static Hpool hpool = { .limit = 16, .peer = 4, .idle = 5, /* seconds */ }; static QLock authlk; static Hauth *hauth; static void hclose(Hconn *h); static int tlstrace(char *fmt, ...) { int r; va_list a; va_start(a, fmt); r = vfprint(2, fmt, a); va_end(a); return r; } static int tlswrap(int fd, char *servername) { TLSconn conn; memset(&conn, 0, sizeof(conn)); if(debug) conn.trace = tlstrace; if(servername != nil) conn.serverName = smprint("%N", servername); if((fd = tlsClient(fd, &conn)) < 0){ if(debug) fprint(2, "tlsClient: %r\n"); } free(conn.cert); free(conn.sessionID); free(conn.serverName); return fd; } static Hconn* hdial(Url *u, int cached) { char addr[128]; Hconn *h, *p; int fd, ctl; snprint(addr, sizeof(addr), "tcp!%s!%s", u->host, u->port ? u->port : u->scheme); qlock(&hpool); if(cached){ for(p = nil, h = hpool.head; h; p = h, h = h->next){ if(strcmp(h->addr, addr) == 0){ if(p) p->next = h->next; else hpool.head = h->next; h->next = nil; qunlock(&hpool); return h; } } } hpool.active++; qunlock(&hpool); if(debug) fprint(2, "hdial [%d] %s\n", hpool.active, addr); if(proxy) snprint(addr, sizeof(addr), "tcp!%s!%s", proxy->host, proxy->port ? proxy->port : proxy->scheme); if((fd = dial(addr, 0, 0, &ctl)) < 0) return nil; if(proxy){ if(strcmp(proxy->scheme, "https") == 0) fd = tlswrap(fd, proxy->host); } else { if(strcmp(u->scheme, "https") == 0) fd = tlswrap(fd, u->host); } if(fd < 0){ close(ctl); return nil; } h = emalloc(sizeof(*h)); h->next = nil; h->time = 0; h->cancel = 0; h->tunnel = 0; h->keep = cached; h->len = 0; h->fd = fd; h->ctl = ctl; if(proxy){ h->tunnel = strcmp(u->scheme, "https") == 0; snprint(addr, sizeof(addr), "tcp!%s!%s", u->host, u->port ? u->port : u->scheme); } nstrcpy(h->addr, addr, sizeof(h->addr)); return h; } static void hcloseall(Hconn *x) { Hconn *h; while(h = x){ x = h->next; h->next = nil; h->keep = 0; hclose(h); } } static void hclose(Hconn *h) { Hconn *x, *t; int i, n; if(h == nil) return; qlock(&hpool); if(!h->tunnel && h->keep && h->fd >= 0){ for(n = 0, i = 0, t = nil, x = hpool.head; x; x = x->next){ if(strcmp(x->addr, h->addr) == 0) if(++n > hpool.peer) break; if(++i < hpool.limit) t = x; } if(x == nil){ /* return connection to pool */ h->time = time(0); h->next = hpool.head; hpool.head = h; /* cut off tail */ if(t){ x = t->next; t->next = nil; } i = h->next != nil; qunlock(&hpool); /* free the tail */ hcloseall(x); /* * if h is first one in pool, spawn proc to close * idle connections. */ if(i == 0) if(rfork(RFMEM|RFPROC|RFNOWAIT) == 0){ do { Hconn **xx; long now; sleep(1000); qlock(&hpool); now = time(0); x = nil; xx = &hpool.head; while(h = *xx){ if((now - h->time) > hpool.idle){ *xx = h->next; /* link to tail */ h->next = x; x = h; continue; } xx = &h->next; } i = hpool.head != nil; qunlock(&hpool); /* free the tail */ hcloseall(x); } while(i); exits(nil); } return; } } hpool.active--; qunlock(&hpool); if(debug) fprint(2, "hclose [%d] %s\n", hpool.active, h->addr); if(h->ctl >= 0) close(h->ctl); if(h->fd >= 0) close(h->fd); free(h); } static void hhangup(Hconn *h) { if(debug) fprint(2, "hangup pc=%p: %r\n", getcallerpc(&h)); h->keep = 0; if(h->ctl >= 0) hangup(h->ctl); } static int hread(Hconn *h, void *data, int len) { if(h->len > 0){ if(len > h->len) len = h->len; memmove(data, h->buf, len); h->len -= len; if(h->len > 0) memmove(h->buf, h->buf + len, h->len); return len; } if((len = read(h->fd, data, len)) == 0) h->keep = 0; if(len < 0) hhangup(h); return len; } static int hwrite(Hconn *h, void *data, int len) { if(write(h->fd, data, len) != len){ hhangup(h); return -1; } return len; } static int hline(Hconn *h, char *data, int len, int cont) { char *x, *y, *e; int n; data[0] = 0; for(;;){ if(h->len > 0){ while(x = memchr(h->buf, '\n', h->len)){ n = x - h->buf; if(n > 0 && x[-1] == '\r') n--; if(n > 0 && cont){ e = h->buf + h->len; for(y = x+1; y < e; y++) if(*y != ' ' && *y != '\t') break; if(y >= e || *y == 0) break; if(y > x+1){ if(x > h->buf && x[-1] == '\r') x--; memmove(x, y, e - y); h->len -= y - x; continue; } } if(n < len) len = n; memmove(data, h->buf, len); data[len] = 0; h->len -= (++x - h->buf); if(h->len > 0) memmove(h->buf, x, h->len); return len; } } n = sizeof(h->buf) - h->len; if(n <= 0) return 0; if(h->tunnel) n = 1; /* do not read beyond header */ if((n = read(h->fd, h->buf + h->len, n)) <= 0){ hhangup(h); return -1; } h->len += n; } } static int hauthgetkey(char *params) { if(debug) fprint(2, "hauthgetkey %s\n", params); werrstr("needkey %s", params); return -1; } int authenticate(Url *u, Url *ru, char *method, char *s) { char oerr[ERRMAX], *user, *pass, *realm, *nonce, *qop, *opaque, *x; Hauth *a; Fmt fmt; int n; snprint(oerr, sizeof(oerr), "authentification failed"); errstr(oerr, sizeof(oerr)); user = u->user; pass = u->pass; realm = nonce = opaque = nil; if(!cistrncmp(s, "Basic ", 6)){ UserPasswd *up; s += 6; if(x = cistrstr(s, "realm=")) realm = unquote(x+6, &s); if(realm == nil) return -1; up = nil; if(user == nil || pass == nil){ fmtstrinit(&fmt); fmtprint(&fmt, " realm=%q", realm); if(user) fmtprint(&fmt, " user=%q", user); if((s = fmtstrflush(&fmt)) == nil) return -1; up = auth_getuserpasswd(hauthgetkey, "proto=pass service=http server=%q%s", u->host, s); free(s); if(up == nil) return -1; user = up->user; pass = up->passwd; } fmtstrinit(&fmt); fmtprint(&fmt, "%s:%s", user ? user : "", pass ? pass : ""); if(up){ memset(up->user, 0, strlen(up->user)); memset(up->passwd, 0, strlen(up->passwd)); free(up); } if((s = fmtstrflush(&fmt)) == nil) return -1; n = strlen(s); fmtstrinit(&fmt); fmtprint(&fmt, "Basic %.*[", n, s); memset(s, 0, n); free(s); u = saneurl(url(".", u)); /* all uris below the requested one */ }else if(!cistrncmp(s, "Digest ", 7)){ char chal[1024], ouser[128], resp[2*MD5LEN+1]; uchar cnonce[16]; uint nc; int nchal; s += 7; if(x = cistrstr(s, "realm=")) realm = unquote(x+6, &s); if(x = cistrstr(s, "nonce=")) nonce = unquote(x+6, &s); if(x = cistrstr(s, "qop=")) qop = unquote(x+4, &s); else qop = ""; if(x = cistrstr(s, "opaque=")) opaque = unquote(x+7, &s); if(realm == nil || nonce == nil) return -1; fmtstrinit(&fmt); fmtprint(&fmt, " realm=%q", realm); if(user) fmtprint(&fmt, " user=%q", user); if((s = fmtstrflush(&fmt)) == nil) return -1; /* RFC2617 "quality of protection" (qop) extension */ if(cistrcmp(qop, "auth") == 0){ static uint counter = 0; nc = ++counter; genrandom(cnonce, sizeof(cnonce)); nchal = snprint(chal, sizeof(chal), "%s:%8.8ud:%.*H:%s %s %U", nonce, nc, sizeof(cnonce), cnonce, qop, method, ru); } else { nc = 0; nchal = snprint(chal, sizeof(chal), "%s %s %U", nonce, method, ru); } n = auth_respond(chal, nchal, ouser, sizeof ouser, resp, sizeof resp, hauthgetkey, "proto=httpdigest role=client server=%q%s", u->host, s); memset(chal, 0, sizeof(chal)); free(s); if(n < 0) return -1; fmtstrinit(&fmt); fmtprint(&fmt, "Digest "); fmtprint(&fmt, "username=\"%s\", ", ouser); fmtprint(&fmt, "realm=\"%s\", ", realm); fmtprint(&fmt, "host=\"%N\", ", u->host); fmtprint(&fmt, "uri=\"%U\", ", ru); fmtprint(&fmt, "nonce=\"%s\", ", nonce); if(cistrcmp(qop, "auth") == 0){ fmtprint(&fmt, "qop=%s, nc=%8.8ud, cnonce=\"%.*H\", ", qop, nc, sizeof(cnonce), cnonce); memset(cnonce, 0, sizeof(cnonce)); } fmtprint(&fmt, "response=\"%.*s\"", n, resp); if(opaque) fmtprint(&fmt, ", opaque=\"%s\"", opaque); u = saneurl(url("/", u)); /* BUG: should be the ones in domain= only */ } else return -1; if((s = fmtstrflush(&fmt)) == nil){ freeurl(u); return -1; } if(u == nil){ free(s); return -1; } a = emalloc(sizeof(*a)); a->url = u; a->auth = s; qlock(&authlk); a->next = hauth; hauth = a; qunlock(&authlk); errstr(oerr, sizeof(oerr)); return 0; } int hauthenticate(Url *u, Url *ru, char *method, char *key, Key *hdr) { for(hdr = getkey(hdr, key); hdr != nil; hdr = getkey(hdr->next, key)) if(authenticate(u, ru, method, hdr->val) == 0) return 0; return -1; } void freeauth(Hauth **a) { Hauth *x = *a; if(x == nil) return; *a = x->next; if(debug) fprint(2, "freeauth for %U\n", x->url); freeurl(x->url); memset(x->auth, 0, strlen(x->auth)); free(x->auth); free(x); } void flushauth(Url *u, char *t) { Hauth **a; for(a = &hauth; *a != nil; ){ if(matchurl(u, (*a)->url) && (t == nil || !strcmp(t, (*a)->auth))){ freeauth(a); continue; } a = &(*a)->next; } } static void catch(void *, char *msg) { if(strstr("alarm", msg) != nil) noted(NCONT); else noted(NDFLT); } #define NOLENGTH 0x7fffffffffffffffLL void http(char *m, Url *u, Key *shdr, Buq *qbody, Buq *qpost) { int i, l, n, try, pid, fd, cfd, needlength, chunked, retry, nobody, badauth; char *s, *x, buf[8192+2], status[256], method[16], *host; vlong length, offset; Url ru, tu, *nu; Key *k, *rhdr; Hconn *h; Hauth **a; incref(qbody); if(qpost) incref(qpost); nstrcpy(method, m, sizeof(method)); switch(rfork(RFPROC|RFMEM|RFNOWAIT)){ default: return; case -1: buclose(qbody, "can't fork"); bufree(qbody); buclose(qpost, "can't fork"); bufree(qpost); while(k = shdr){ shdr = k->next; free(k); } freeurl(u); return; case 0: break; } notify(catch); if(qpost){ /* file for spooling the postbody if we need to restart the request */ snprint(buf, sizeof(buf), "/tmp/http.%d.%d.post", getppid(), getpid()); fd = create(buf, OEXCL|ORDWR|ORCLOSE, 0600); } else fd = -1; h = nil; cfd = -1; pid = 0; host = nil; needlength = 0; badauth = 0; for(try = 0; try < 12; try++){ strcpy(status, "0 No status"); if(u == nil || (strcmp(u->scheme, "http") && strcmp(u->scheme, "https"))){ werrstr("bad url scheme"); break; } if(debug) fprint(2, "http(%d): %s %U\n", try, method, u); /* preemptive authentication from hauth cache */ qlock(&authlk); if(proxy && !lookkey(shdr, "Proxy-Authorization")) for(a = &hauth; *a != nil; a = &(*a)->next) if(matchurl((*a)->url, proxy)){ shdr = addkey(shdr, "Proxy-Authorization", (*a)->auth); if(strncmp((*a)->auth, "Digest ", 7) == 0) freeauth(a); break; } if(!lookkey(shdr, "Authorization")) for(a = &hauth; *a != nil; a = &(*a)->next) if(matchurl((*a)->url, u)){ shdr = addkey(shdr, "Authorization", (*a)->auth); if(strncmp((*a)->auth, "Digest ", 7) == 0) freeauth(a); break; } qunlock(&authlk); length = 0; chunked = 0; if(qpost){ /* have to read it to temp file to figure out the length */ if(fd >= 0 && needlength && lookkey(shdr, "Content-Length") == nil){ seek(fd, 0, 2); while((n = buread(qpost, buf, sizeof(buf))) > 0) write(fd, buf, n); shdr = delkey(shdr, "Transfer-Encoding"); } qlock(qpost); /* wait until buffer is full, most posts are small */ while(!qpost->closed && qpost->size < qpost->limit && qpost->nwq == 0) rsleep(&qpost->rz); if(lookkey(shdr, "Content-Length")) chunked = 0; else if(x = lookkey(shdr, "Transfer-Encoding")) chunked = cistrstr(x, "chunked") != nil; else if(chunked = !qpost->closed) shdr = addkey(shdr, "Transfer-Encoding", "chunked"); else if(qpost->closed){ if(fd >= 0){ length = seek(fd, 0, 2); if(length < 0) length = 0; } length += qpost->size; snprint(buf, sizeof(buf), "%lld", length); shdr = addkey(shdr, "Content-Length", buf); } qunlock(qpost); } /* http requires ascii encoding of host */ free(host); host = smprint("%N", u->host); if(proxy && strcmp(u->scheme, "https") != 0){ ru = *u; ru.host = host; ru.fragment = nil; } else { memset(&ru, 0, sizeof(ru)); ru.path = Upath(u); ru.query = u->query; } n = snprint(buf, sizeof(buf), "%s %U HTTP/1.1\r\nHost: %]%s%s\r\n", method, &ru, host, u->port ? ":" : "", u->port ? u->port : ""); if(n >= sizeof(buf)-64){ werrstr("request too large"); break; } if(h == nil){ alarm(timeout); if((h = hdial(u, qpost==nil)) == nil) break; } if(h->tunnel){ n = snprint(buf, sizeof(buf), "CONNECT %]:%s HTTP/1.1\r\nHost: %]:%s\r\n", host, u->port ? u->port : "443", host, u->port ? u->port : "443"); } else if((cfd = open("/mnt/webcookies/http", ORDWR)) >= 0){ /* only scheme, host and path are relevant for cookies */ memset(&tu, 0, sizeof(tu)); tu.scheme = u->scheme; tu.host = host; tu.path = Upath(u); fprint(cfd, "%U", &tu); for(;;){ if(n >= sizeof(buf)-2){ if(debug) fprint(2, "-> %.*s", utfnlen(buf, n), buf); if(hwrite(h, buf, n) != n) goto Badflush; n = 0; } if((l = read(cfd, buf+n, sizeof(buf)-2 - n)) == 0) break; if(l < 0){ close(cfd); cfd = -1; break; } n += l; } } for(k = shdr; k; k = k->next){ /* only send proxy headers when establishing tunnel */ if(h->tunnel && cistrncmp(k->key, "Proxy-", 6) != 0) continue; if(n > 0){ if(debug) fprint(2, "-> %.*s", utfnlen(buf, n), buf); if(hwrite(h, buf, n) != n) goto Badflush; } n = snprint(buf, sizeof(buf)-2, "%s: %s\r\n", k->key, k->val); } n += snprint(buf+n, sizeof(buf)-n, "\r\n"); if(debug) fprint(2, "-> %.*s", utfnlen(buf, n), buf); if(hwrite(h, buf, n) != n){ Badflush: alarm(0); goto Retry; } if(qpost && !h->tunnel){ h->cancel = 0; if((pid = rfork(RFMEM|RFPROC)) <= 0){ int ifd; if((ifd = fd) >= 0) seek(ifd, 0, 0); while(!h->cancel){ alarm(0); if((ifd < 0) || ((n = read(ifd, buf, sizeof(buf)-2)) <= 0)){ ifd = -1; if((n = buread(qpost, buf, sizeof(buf)-2)) <= 0) break; if(fd >= 0) if(write(fd, buf, n) != n) break; } alarm(timeout); if(chunked){ char tmp[32]; if(hwrite(h, tmp, snprint(tmp, sizeof(tmp), "%x\r\n", n)) < 0) break; buf[n++] = '\r'; buf[n++] = '\n'; } if(hwrite(h, buf, n) != n) break; } if(chunked){ alarm(timeout); hwrite(h, "0\r\n\r\n", 5); }else h->keep = 0; if(pid == 0) exits(nil); } /* no timeout when posting */ alarm(0); } else alarm(timeout); Cont: rhdr = 0; retry = 0; chunked = 0; offset = 0; length = NOLENGTH; for(l = 0; hline(h, s = buf, sizeof(buf)-1, 1) > 0; l++){ if(debug) fprint(2, "<- %s\n", s); if(l == 0){ if(x = strchr(s, ' ')) while(*x == ' ') *x++ = 0; if(cistrncmp(s, "HTTP", 4)){ h->keep = 0; if(cistrcmp(s, "ICY")) break; } if(x[0]) nstrcpy(status, x, sizeof(status)); continue; } if((k = parsehdr(s)) == nil) continue; if(!cistrcmp(k->key, "Connection")){ if(cistrstr(k->val, "close")) h->keep = 0; } else if(!cistrcmp(k->key, "Content-Length")) length = atoll(k->val); else if(!cistrcmp(k->key, "Transfer-Encoding")){ if(cistrstr(k->val, "chunked")) chunked = 1; } else if(!cistrcmp(k->key, "Set-Cookie") || !cistrcmp(k->key, "Set-Cookie2")){ if(cfd >= 0) fprint(cfd, "Set-Cookie: %s\n", k->val); free(k); continue; } k->next = rhdr; rhdr = k; } alarm(0); if(cfd >= 0){ close(cfd); cfd = -1; } nobody = !cistrcmp(method, "HEAD"); if((i = atoi(status)) < 0) i = 0; Status: switch(i){ default: if(i % 100){ i -= (i % 100); goto Status; } goto Error; case 100: /* Continue */ case 101: /* Switching Protocols */ case 102: /* Processing */ case 103: /* Early Hints */ while(k = rhdr){ rhdr = k->next; free(k); } strcpy(status, "0 No status"); goto Cont; case 304: /* Not Modified */ nobody = 1; case 305: /* Use Proxy */ case 400: /* Bad Request */ case 402: /* Payment Required */ case 403: /* Forbidden */ case 404: /* Not Found */ case 405: /* Method Not Allowed */ case 406: /* Not Acceptable */ case 408: /* Request Timeout */ case 409: /* Conflict */ case 410: /* Gone */ goto Error; case 411: /* Length Required */ if(qpost){ needlength = 1; h->cancel = 1; retry = 1; break; } case 412: /* Precondition Failed */ case 413: /* Request Entity Too Large */ case 414: /* Request URI Too Large */ case 415: /* Unsupported Media Type */ case 416: /* Requested Range Not Satisfiable */ case 417: /* Expectation Failed */ case 500: /* Internal server error */ case 501: /* Not implemented */ case 502: /* Bad gateway */ case 503: /* Service unavailable */ case 504: /* Gateway Timeout */ case 505: /* HTTP Version not Supported */ Error: h->cancel = 1; buclose(qbody, status); buclose(qpost, status); break; case 300: /* Multiple choices */ case 302: /* Found */ case 303: /* See Other */ if(qpost){ if(pid > 0){ waitpid(); pid = 0; } buclose(qpost, 0); bufree(qpost); qpost = nil; } shdr = delkey(shdr, "Content-Length"); shdr = delkey(shdr, "Content-Type"); shdr = delkey(shdr, "Transfer-Encoding"); if(cistrcmp(method, "HEAD")) nstrcpy(method, "GET", sizeof(method)); case 301: /* Moved Permanently */ case 307: /* Temporary Redirect */ case 308: /* Resume Incomplete */ if((x = lookkey(rhdr, "Location")) == nil) goto Error; if((nu = saneurl(url(x, u))) == nil) goto Error; freeurl(u); u = nu; if(0){ case 401: /* Unauthorized */ if(x = lookkey(shdr, "Authorization")){ qlock(&authlk); flushauth(nil, x); qunlock(&authlk); if(badauth++) goto Error; } if(hauthenticate(u, &ru, method, "WWW-Authenticate", rhdr) < 0){ Autherror: h->cancel = 1; rerrstr(buf, sizeof(buf)); buclose(qbody, buf); buclose(qpost, buf); break; } } if(0){ case 407: /* Proxy Auth */ if(proxy == nil) goto Error; if(x = lookkey(shdr, "Proxy-Authorization")){ qlock(&authlk); flushauth(proxy, x); qunlock(&authlk); if(badauth++) goto Error; } if(hauthenticate(proxy, proxy, method, "Proxy-Authenticate", rhdr) < 0) goto Autherror; } case 0: /* No status */ if(qpost && fd < 0){ if(i > 0) goto Error; break; } h->cancel = 1; retry = 1; break; case 204: /* No Content */ case 205: /* Reset Content */ nobody = 1; case 200: /* OK */ case 201: /* Created */ case 202: /* Accepted */ case 203: /* Non-Authoritative Information */ case 206: /* Partial Content */ if(h->tunnel) break; qbody->url = u; u = nil; qbody->hdr = rhdr; rhdr = nil; if(nobody) buclose(qbody, 0); break; } while(k = rhdr){ rhdr = k->next; free(k); } /* * remove authorization headers so on the next round, we use * the hauth cache (wich checks the scope url). this makes * sure we wont send credentials to the wrong url after * a redirect. */ shdr = delkey(shdr, "Proxy-Authorization"); shdr = delkey(shdr, "Authorization"); /* * when 2xx response is given for the CONNECT request * then the proxy server has established the connection. */ if(h->tunnel && !retry && (i/100) == 2){ if((h->fd = tlswrap(h->fd, host)) < 0) break; /* proceed to the original request */ h->tunnel = 0; continue; } if(!chunked && length == NOLENGTH) h->keep = 0; /* * read the response body (if any). retry means we'r just * skipping the error page so we wont touch qbody. */ while(!nobody){ if((qbody->closed || retry) && !h->keep) break; if(chunked){ if(hline(h, buf, sizeof(buf)-1, 0) <= 0) break; length = strtoll(buf, nil, 16); offset = 0; } while(offset < length){ l = sizeof(buf); if(l > (length - offset)) l = (length - offset); if((n = hread(h, buf, l)) <= 0) break; offset += n; if(!retry) if(buwrite(qbody, buf, n) != n) break; } if(offset != length){ h->keep = 0; if(length != NOLENGTH) break; } if(chunked){ while(hline(h, buf, sizeof(buf)-1, 1) > 0){ if(debug) fprint(2, "<= %s\n", buf); if(!retry) if(k = parsehdr(buf)){ k->next = qbody->hdr; qbody->hdr = k; } } if(length > 0) continue; } if(!retry) buclose(qbody, 0); break; } if(!retry) break; Retry: if(cfd >= 0) close(cfd); if(pid > 0){ waitpid(); pid = 0; } hclose(h); h = nil; } alarm(0); snprint(buf, sizeof(buf), "%s %r", status); buclose(qbody, buf); bufree(qbody); if(qpost){ if(pid > 0) waitpid(); buclose(qpost, buf); bufree(qpost); } if(fd >= 0) close(fd); hclose(h); freeurl(u); free(host); while(k = shdr){ shdr = k->next; free(k); } exits(nil); }