diff options
| -rw-r--r-- | src/network/res_msend.c | 119 |
1 files changed, 117 insertions, 2 deletions
diff --git a/src/network/res_msend.c b/src/network/res_msend.c index 98e6d8a3..1e76886a 100644 --- a/src/network/res_msend.c +++ b/src/network/res_msend.c @@ -1,5 +1,6 @@ #include <sys/socket.h> #include <netinet/in.h> +#include <netinet/tcp.h> #include <netdb.h> #include <arpa/inet.h> #include <stdint.h> @@ -29,6 +30,51 @@ static unsigned long mtime() + ts.tv_nsec / 1000000; } +static int start_tcp(struct pollfd *pfd, int family, const void *sa, socklen_t sl, const unsigned char *q, int ql) +{ + struct msghdr mh = { + .msg_name = (void *)sa, + .msg_namelen = sl, + .msg_iovlen = 2, + .msg_iov = (struct iovec [2]){ + { .iov_base = (uint8_t[]){ ql>>8, ql }, .iov_len = 2 }, + { .iov_base = (void *)q, .iov_len = ql } } + }; + int r; + int fd = socket(family, SOCK_STREAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0); + pfd->fd = fd; + pfd->events = POLLOUT; + if (!setsockopt(fd, IPPROTO_TCP, TCP_FASTOPEN_CONNECT, + &(int){1}, sizeof(int))) { + r = sendmsg(fd, &mh, MSG_FASTOPEN|MSG_NOSIGNAL); + if (r == ql+2) pfd->events = POLLIN; + if (r >= 0) return r; + if (errno == EINPROGRESS) return 0; + } + r = connect(fd, sa, sl); + if (!r || errno == EINPROGRESS) return 0; + close(fd); + pfd->fd = -1; + return -1; +} + +static void step_mh(struct msghdr *mh, size_t n) +{ + /* Adjust iovec in msghdr to skip first n bytes. */ + while (mh->msg_iovlen && n >= mh->msg_iov->iov_len) { + n -= mh->msg_iov->iov_len; + mh->msg_iov++; + mh->msg_iovlen--; + } + if (!mh->msg_iovlen) return; + mh->msg_iov->iov_base = (char *)mh->msg_iov->iov_base + n; + mh->msg_iov->iov_len -= n; +} + +/* Internal contract for __res_msend[_rc]: asize must be >=512, nqueries + * must be sufficiently small to be safe as VLA size. In practice it's + * either 1 or 2, anyway. */ + int __res_msend_rc(int nqueries, const unsigned char *const *queries, const int *qlens, unsigned char *const *answers, int *alens, int asize, const struct resolvconf *conf) @@ -47,6 +93,9 @@ int __res_msend_rc(int nqueries, const unsigned char *const *queries, int i, j; int cs; struct pollfd pfd[nqueries+2]; + int qpos[nqueries], apos[nqueries]; + unsigned char alen_buf[nqueries][2]; + int r; unsigned long t0, t1, t2; pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs); @@ -125,6 +174,11 @@ int __res_msend_rc(int nqueries, const unsigned char *const *queries, t1 = t2 - retry_interval; for (; t2-t0 < timeout; t2=mtime()) { + /* This is the loop exit condition: that all queries + * have an accepted answer. */ + for (i=0; i<nqueries && alens[i]>0; i++); + if (i==nqueries) break; + if (t2-t1 >= retry_interval) { /* Query all configured namservers in parallel */ for (i=0; i<nqueries; i++) @@ -140,7 +194,8 @@ int __res_msend_rc(int nqueries, const unsigned char *const *queries, /* Wait for a response, or until time to retry */ if (poll(pfd, nqueries+1, t1+retry_interval-t2) <= 0) continue; - while ((rlen = recvfrom(fd, answers[next], asize, 0, + while (next < nqueries && + (rlen = recvfrom(fd, answers[next], asize, 0, (void *)&sa, (socklen_t[1]){sl})) >= 0) { /* Ignore non-identifiable packets */ @@ -181,12 +236,72 @@ int __res_msend_rc(int nqueries, const unsigned char *const *queries, else memcpy(answers[i], answers[next], rlen); - if (next == nqueries) goto out; + /* Ignore further UDP if all slots full or TCP-mode */ + if (next == nqueries) pfd[nqueries].events = 0; + + /* If answer is truncated (TC bit), fallback to TCP */ + if (answers[i][2] & 2) { + alens[i] = -1; + pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, 0); + r = start_tcp(pfd+i, family, ns+j, sl, queries[i], qlens[i]); + pthread_setcancelstate(cs, 0); + if (r >= 0) { + qpos[i] = r; + apos[i] = 0; + } + continue; + } + } + + for (i=0; i<nqueries; i++) if (pfd[i].revents & POLLOUT) { + struct msghdr mh = { + .msg_iovlen = 2, + .msg_iov = (struct iovec [2]){ + { .iov_base = (uint8_t[]){ qlens[i]>>8, qlens[i] }, .iov_len = 2 }, + { .iov_base = (void *)queries[i], .iov_len = qlens[i] } } + }; + step_mh(&mh, qpos[i]); + r = sendmsg(pfd[i].fd, &mh, MSG_NOSIGNAL); + if (r < 0) goto out; + qpos[i] += r; + if (qpos[i] == qlens[i]+2) + pfd[i].events = POLLIN; + } + + for (i=0; i<nqueries; i++) if (pfd[i].revents & POLLIN) { + struct msghdr mh = { + .msg_iovlen = 2, + .msg_iov = (struct iovec [2]){ + { .iov_base = alen_buf[i], .iov_len = 2 }, + { .iov_base = answers[i], .iov_len = asize } } + }; + step_mh(&mh, apos[i]); + r = recvmsg(pfd[i].fd, &mh, 0); + if (r < 0) goto out; + apos[i] += r; + if (apos[i] < 2) continue; + int alen = alen_buf[i][0]*256 + alen_buf[i][1]; + if (alen < 13) goto out; + if (apos[i] < alen+2 && apos[i] < asize+2) + continue; + int rcode = answers[i][3] & 15; + if (rcode != 0 && rcode != 3) + goto out; + + /* Storing the length here commits the accepted answer. + * Immediately close TCP socket so as not to consume + * resources we no longer need. */ + alens[i] = alen; + __syscall(SYS_close, pfd[i].fd); + pfd[i].fd = -1; } } out: pthread_cleanup_pop(1); + /* Disregard any incomplete TCP results */ + for (i=0; i<nqueries; i++) if (alens[i]<0) alens[i] = 0; + return 0; } |