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-rw-r--r--src/network/res_msend.c325
1 files changed, 325 insertions, 0 deletions
diff --git a/src/network/res_msend.c b/src/network/res_msend.c
new file mode 100644
index 0000000..86c2fcf
--- /dev/null
+++ b/src/network/res_msend.c
@@ -0,0 +1,325 @@
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <netinet/tcp.h>
+#include <netdb.h>
+#include <arpa/inet.h>
+#include <stdint.h>
+#include <string.h>
+#include <poll.h>
+#include <time.h>
+#include <ctype.h>
+#include <unistd.h>
+#include <errno.h>
+#include <pthread.h>
+#include "stdio_impl.h"
+#include "syscall.h"
+#include "lookup.h"
+
+static void cleanup(void *p)
+{
+ struct pollfd *pfd = p;
+ for (int i=0; pfd[i].fd >= -1; i++)
+ if (pfd[i].fd >= 0) __syscall(SYS_close, pfd[i].fd);
+}
+
+static unsigned long mtime()
+{
+ struct timespec ts;
+ if (clock_gettime(CLOCK_MONOTONIC, &ts) < 0 && errno == ENOSYS)
+ clock_gettime(CLOCK_REALTIME, &ts);
+ return (unsigned long)ts.tv_sec * 1000
+ + 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)
+{
+ int fd;
+ int timeout, attempts, retry_interval, servfail_retry;
+ union {
+ struct sockaddr_in sin;
+ struct sockaddr_in6 sin6;
+ } sa = {0}, ns[MAXNS] = {{0}};
+ socklen_t sl = sizeof sa.sin;
+ int nns = 0;
+ int family = AF_INET;
+ int rlen;
+ int next;
+ 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);
+
+ timeout = 1000*conf->timeout;
+ attempts = conf->attempts;
+
+ for (nns=0; nns<conf->nns; nns++) {
+ const struct address *iplit = &conf->ns[nns];
+ if (iplit->family == AF_INET) {
+ memcpy(&ns[nns].sin.sin_addr, iplit->addr, 4);
+ ns[nns].sin.sin_port = htons(53);
+ ns[nns].sin.sin_family = AF_INET;
+ } else {
+ sl = sizeof sa.sin6;
+ memcpy(&ns[nns].sin6.sin6_addr, iplit->addr, 16);
+ ns[nns].sin6.sin6_port = htons(53);
+ ns[nns].sin6.sin6_scope_id = iplit->scopeid;
+ ns[nns].sin6.sin6_family = family = AF_INET6;
+ }
+ }
+
+ /* Get local address and open/bind a socket */
+ fd = socket(family, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
+
+ /* Handle case where system lacks IPv6 support */
+ if (fd < 0 && family == AF_INET6 && errno == EAFNOSUPPORT) {
+ for (i=0; i<nns && conf->ns[nns].family == AF_INET6; i++);
+ if (i==nns) {
+ pthread_setcancelstate(cs, 0);
+ return -1;
+ }
+ fd = socket(AF_INET, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
+ family = AF_INET;
+ sl = sizeof sa.sin;
+ }
+
+ /* Convert any IPv4 addresses in a mixed environment to v4-mapped */
+ if (fd >= 0 && family == AF_INET6) {
+ setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, &(int){0}, sizeof 0);
+ for (i=0; i<nns; i++) {
+ if (ns[i].sin.sin_family != AF_INET) continue;
+ memcpy(ns[i].sin6.sin6_addr.s6_addr+12,
+ &ns[i].sin.sin_addr, 4);
+ memcpy(ns[i].sin6.sin6_addr.s6_addr,
+ "\0\0\0\0\0\0\0\0\0\0\xff\xff", 12);
+ ns[i].sin6.sin6_family = AF_INET6;
+ ns[i].sin6.sin6_flowinfo = 0;
+ ns[i].sin6.sin6_scope_id = 0;
+ }
+ }
+
+ sa.sin.sin_family = family;
+ if (fd < 0 || bind(fd, (void *)&sa, sl) < 0) {
+ if (fd >= 0) close(fd);
+ pthread_setcancelstate(cs, 0);
+ return -1;
+ }
+
+ /* Past this point, there are no errors. Each individual query will
+ * yield either no reply (indicated by zero length) or an answer
+ * packet which is up to the caller to interpret. */
+
+ for (i=0; i<nqueries; i++) pfd[i].fd = -1;
+ pfd[nqueries].fd = fd;
+ pfd[nqueries].events = POLLIN;
+ pfd[nqueries+1].fd = -2;
+
+ pthread_cleanup_push(cleanup, pfd);
+ pthread_setcancelstate(cs, 0);
+
+ memset(alens, 0, sizeof *alens * nqueries);
+
+ retry_interval = timeout / attempts;
+ next = 0;
+ t0 = t2 = mtime();
+ 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++)
+ if (!alens[i])
+ for (j=0; j<nns; j++)
+ sendto(fd, queries[i],
+ qlens[i], MSG_NOSIGNAL,
+ (void *)&ns[j], sl);
+ t1 = t2;
+ servfail_retry = 2 * nqueries;
+ }
+
+ /* Wait for a response, or until time to retry */
+ if (poll(pfd, nqueries+1, t1+retry_interval-t2) <= 0) continue;
+
+ while (next < nqueries) {
+ struct msghdr mh = {
+ .msg_name = (void *)&sa,
+ .msg_namelen = sl,
+ .msg_iovlen = 1,
+ .msg_iov = (struct iovec []){
+ { .iov_base = (void *)answers[next],
+ .iov_len = asize }
+ }
+ };
+ rlen = recvmsg(fd, &mh, 0);
+ if (rlen < 0) break;
+
+ /* Ignore non-identifiable packets */
+ if (rlen < 4) continue;
+
+ /* Ignore replies from addresses we didn't send to */
+ for (j=0; j<nns && memcmp(ns+j, &sa, sl); j++);
+ if (j==nns) continue;
+
+ /* Find which query this answer goes with, if any */
+ for (i=next; i<nqueries && (
+ answers[next][0] != queries[i][0] ||
+ answers[next][1] != queries[i][1] ); i++);
+ if (i==nqueries) continue;
+ if (alens[i]) continue;
+
+ /* Only accept positive or negative responses;
+ * retry immediately on server failure, and ignore
+ * all other codes such as refusal. */
+ switch (answers[next][3] & 15) {
+ case 0:
+ case 3:
+ break;
+ case 2:
+ if (servfail_retry && servfail_retry--)
+ sendto(fd, queries[i],
+ qlens[i], MSG_NOSIGNAL,
+ (void *)&ns[j], sl);
+ default:
+ continue;
+ }
+
+ /* Store answer in the right slot, or update next
+ * available temp slot if it's already in place. */
+ alens[i] = rlen;
+ if (i == next)
+ for (; next<nqueries && alens[next]; next++);
+ else
+ memcpy(answers[i], answers[next], rlen);
+
+ /* 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) || (mh.msg_flags & MSG_TRUNC)) {
+ 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;
+}
+
+int __res_msend(int nqueries, const unsigned char *const *queries,
+ const int *qlens, unsigned char *const *answers, int *alens, int asize)
+{
+ struct resolvconf conf;
+ if (__get_resolv_conf(&conf, 0, 0) < 0) return -1;
+ return __res_msend_rc(nqueries, queries, qlens, answers, alens, asize, &conf);
+}
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