1 files changed, 372 insertions, 0 deletions

diff --git a/src/libs6dns/s6dns_engine.c b/src/libs6dns/s6dns_engine.c
new file mode 100644
index 0000000..4145ef7
--- /dev/null
+++ b/src/libs6dns/s6dns_engine.c
@@ -0,0 +1,372 @@
+/* ISC license. */
+
+#include <errno.h>
+#include <skalibs/uint16.h>
+#include <skalibs/uint32.h>
+#include <skalibs/allreadwrite.h>
+#include <skalibs/bytestr.h>
+#include <skalibs/error.h>
+#include <skalibs/tai.h>
+#include <skalibs/stralloc.h>
+#include <skalibs/mininetstring.h>
+#include <skalibs/socket.h>
+#include <skalibs/djbunix.h>
+#include <skalibs/ip46.h>
+#include <skalibs/random.h>
+#include <s6-dns/s6dns-constants.h>
+#include <s6-dns/s6dns-message-internal.h>
+#include <s6-dns/s6dns-message.h>
+#include <s6-dns/s6dns-engine.h>
+
+
+ /* Utility functions */
+
+static inline int qdomain_diff (char const *s1, unsigned int n1, char const *s2, unsigned int n2)
+{
+  return (n1 < n2) ? -1 : (n1 > n2) ? 1 : case_diffb(s1, n1, s2) ;
+}
+
+static int relevant (char const *q, unsigned int qlen, char const *ans, unsigned int anslen, int strict)
+{
+  {
+    s6dns_message_header_t h ;
+    uint16 id ;
+    s6dns_message_header_unpack(ans, &h) ;
+    if (!h.qr || h.opcode || h.z || (h.counts.qd != 1)) return 0 ;
+    if (h.rd != (q[2] & 1)) return 0 ;
+    if (strict && !h.aa && !(q[2] & 1)) return 0 ;
+    uint16_unpack_big(q, &id) ;
+    if (id != h.id) return 0 ;
+  }
+  {
+    char buf[255] ;
+    unsigned int pos = 12 ;
+    unsigned int n = s6dns_message_get_domain_internal(buf, 255, ans, anslen, &pos) ;
+    if (!n) return -1 ;
+    if (pos + 4 > anslen) return (errno = EPROTO, -1) ;
+    if (qdomain_diff(buf, n, q + 12, qlen - 16)) return 0 ;
+    if (byte_diff(q + qlen - 4, 4, ans + pos)) return 0 ;
+  }
+  return 1 ;
+}
+
+
+ /* Network core functions: transport-dependent */
+
+#ifdef SKALIBS_IPV6_ENABLED
+# define socketbind46(fd, ip, port, flag) ((flag) ? socket_bind6(fd, ip, port) : socket_bind4(fd, ip, port))
+# define socketudp46(flag) ((flag) ? socket_udp6() : socket_udp4())
+# define sockettcp46(flag) ((flag) ? socket_tcp6() : socket_tcp4())
+# define socketconnect46(fd, ip, port, flag) ((flag) ? socket_connect6(fd, ip, port) : socket_connect4(fd, ip, port))
+# define S6DNS_ENGINE_LOCAL0 IP6_ANY
+#else
+# define socketbind46(fd, ip, port, flag) ((void)(flag), socket_bind4(fd, ip, port))
+# define socketudp46(flag) socket_udp4()
+# define sockettcp46(flag) socket_tcp4()
+# define socketconnect46(fd, ip, port, flag) socket_connect4(fd, ip, port)
+# define S6DNS_ENGINE_LOCAL0 "\0\0\0"
+#endif
+ 
+static int randombind (int fd, int flag)
+{
+  register unsigned int i = 0 ;
+  for (; i < 10 ; i++)
+    if (socketbind46(fd, S6DNS_ENGINE_LOCAL0, 1025 + badrandom_int(64510), flag) >= 0) return 1 ;
+  return (socketbind46(fd, S6DNS_ENGINE_LOCAL0, 0, flag) >= 0) ;
+}
+
+static int thisudp (s6dns_engine_t *dt, tain_t const *stamp)
+{
+  for (;; dt->curserver++)
+  {
+    if (dt->curserver >= S6DNS_MAX_SERVERS)
+    {
+      dt->curserver = 0 ;
+      if (++dt->protostate >= 4) return -1 ;
+    }
+    if (byte_diff(s6dns_ip46list_ip(&dt->servers, dt->curserver), SKALIBS_IP_SIZE, S6DNS_ENGINE_LOCAL0)) break ;
+  }
+  if (badrandom_string(dt->sa.s + 2, 2) < 2) return 0 ; /* random query id */
+  dt->fd = socketudp46(s6dns_ip46list_is6(&dt->servers, dt->curserver)) ;
+  if (dt->fd < 0) return 0 ;
+  if (!randombind(dt->fd, s6dns_ip46list_is6(&dt->servers, dt->curserver))) goto err ; /* random source port */
+  if ((socketconnect46(dt->fd, s6dns_ip46list_ip(&dt->servers, dt->curserver), 53, s6dns_ip46list_is6(&dt->servers, dt->curserver)) < 0)
+   && (errno != EINPROGRESS)) goto err ;
+  tain_add(&dt->localdeadline, stamp, &tain_infinite_relative) ;
+  dt->flagreading = 0 ;
+  dt->flagwriting = 1 ;
+  if (dt->debughook && dt->debughook->pre_send) (*dt->debughook->pre_send)(dt, dt->debughook->external) ;
+  return 1 ;
+ err:
+  {
+    register int e = errno ;
+    fd_close(dt->fd) ; dt->fd = -1 ;
+    errno = e ;
+  }
+  return 0 ;
+}
+
+static int thistcp (s6dns_engine_t *dt, tain_t const *stamp)
+{
+  for (; dt->curserver < S6DNS_MAX_SERVERS ; dt->curserver++)
+    if (byte_diff(s6dns_ip46list_ip(&dt->servers, dt->curserver), SKALIBS_IP_SIZE, S6DNS_ENGINE_LOCAL0)) break ;
+  if (dt->curserver >= S6DNS_MAX_SERVERS) return -1 ;
+  if (badrandom_string(dt->sa.s + 2, 2) < 2) return 0 ; /* random query id */
+  dt->fd = sockettcp46(s6dns_ip46list_is6(&dt->servers, dt->curserver)) ;
+  if (dt->fd < 0) return 0 ;
+  if (!randombind(dt->fd, s6dns_ip46list_is6(&dt->servers, dt->curserver))) goto err ; /* random source port */
+  if ((socketconnect46(dt->fd, s6dns_ip46list_ip(&dt->servers, dt->curserver), 53, s6dns_ip46list_is6(&dt->servers, dt->curserver)) < 0)
+   && (errno != EINPROGRESS)) goto err ;
+  tain_addsec(&dt->localdeadline, stamp, 10) ;
+  dt->protostate = 0 ;
+  dt->flagtcp = dt->flagconnecting = dt->flagwriting = 1 ;
+  dt->flagreading = 0 ;
+  if (dt->debughook && dt->debughook->pre_send) (*dt->debughook->pre_send)(dt, dt->debughook->external) ;
+  return 1 ;
+ err:
+  {
+    register int e = errno ;
+    fd_close(dt->fd) ; dt->fd = -1 ;
+    errno = e ;
+  }
+  return 0 ;
+}
+
+
+ /* all the rest is transport-agnostic */
+
+static int s6dns_engine_prepare (s6dns_engine_t *dt, tain_t const *stamp, int istcp)
+{
+  for (;; dt->curserver++)
+    switch (istcp ? thistcp(dt, stamp) : thisudp(dt, stamp))
+    {
+      case -1 : return (errno = ENETUNREACH, 0) ;
+      case 0 : break ;
+      case 1 : return 1 ;
+      default : return (errno = EDOM, 0) ; /* can't happen */
+    }
+}
+
+static void prepare_next (s6dns_engine_t *dt, tain_t const *stamp, int istcp)
+{
+  if (!error_isagain(errno))
+  {
+    fd_close(dt->fd) ;
+    dt->curserver++ ;
+    if (s6dns_engine_prepare(dt, stamp, istcp)) errno = EAGAIN ;
+  }
+}
+
+static int s6dns_engine_write_udp (s6dns_engine_t *dt, tain_t const *stamp)
+{
+  static unsigned int const s6dns_engine_udp_timeouts[4] = { 1, 3, 11, 45 } ;
+  if (fd_send(dt->fd, dt->sa.s + 2, dt->querylen - 2, 0) < (int)(dt->querylen - 2))
+    return (prepare_next(dt, stamp, 0), 0) ;
+  tain_addsec(&dt->localdeadline, stamp, s6dns_engine_udp_timeouts[dt->protostate]) ;
+  dt->flagwriting = 0 ;
+  dt->flagreading = 1 ;
+  if (dt->debughook && dt->debughook->post_send) (*dt->debughook->post_send)(dt, dt->debughook->external) ;
+  return (errno = EAGAIN, 1) ;
+}
+
+static int s6dns_engine_write_tcp (s6dns_engine_t *dt, tain_t const *stamp)
+{
+  unsigned int r ;
+  r = allwrite(dt->fd, dt->sa.s + dt->protostate, dt->querylen - dt->protostate) ;
+  dt->protostate += r ;
+  if (r) dt->flagconnecting = 0 ;
+  if (dt->protostate < dt->sa.len)
+  {
+    if ((errno == ECONNRESET) && dt->flagconnecting) errno = EAGAIN ;
+    prepare_next(dt, stamp, 1) ;
+    return 0 ;
+  }
+  dt->protostate = 0 ;
+  tain_addsec(&dt->localdeadline, stamp, 10) ;
+  dt->flagwriting = 0 ;
+  dt->flagreading = 1 ;
+  if (dt->debughook && dt->debughook->post_send) (*dt->debughook->post_send)(dt, dt->debughook->external) ;
+  return (errno = EAGAIN, 1) ;
+}
+
+static int s6dns_engine_read_udp (s6dns_engine_t *dt, tain_t const *stamp)
+{
+  s6dns_message_header_t h ;
+  char buf[513] ;
+  register int r = fd_recv(dt->fd, buf, 513, 0) ;
+  if (r < 0) return (prepare_next(dt, stamp, 0), 0) ;
+  if ((r > 512) || (r < 12)) return (errno = EAGAIN, 0) ;
+  switch (relevant(dt->sa.s + 2, dt->querylen - 2, buf, r, dt->flagstrict))
+  {
+    case -1 : if (!dt->flagstrict) prepare_next(dt, stamp, 0) ; return 0 ;
+    case 0 : return (errno = EAGAIN, 0) ;
+    case 1 : break ;
+    default : return (errno = EDOM, 0) ; /* can't happen */
+  }
+  if (dt->debughook && dt->debughook->post_recv)
+  {
+    if (!stralloc_catb(&dt->sa, buf, r)) return 0 ;
+    (*dt->debughook->post_recv)(dt, dt->debughook->external) ;
+    dt->sa.len = dt->querylen ;
+  }
+  s6dns_message_header_unpack(buf, &h) ;
+  if (h.tc)
+  {
+    fd_close(dt->fd) ;
+    dt->curserver = 0 ;
+    dt->protostate = 0 ;
+    if (s6dns_engine_prepare(dt, stamp, 1)) errno = EAGAIN ;
+    return 0 ;
+  }
+  switch (h.rcode)
+  {
+    case 0 : case 3 : break ; /* normal operation */
+    case 1 : case 4 : case 5 :
+      byte_zero(s6dns_ip46list_ip(&dt->servers, dt->curserver), SKALIBS_IP_SIZE) ; /* do not query it again */
+    default : prepare_next(dt, stamp, 0) ; return 0 ;
+  }
+  if (!stralloc_copyb(&dt->sa, buf, r))
+  {
+    register int e = errno ;
+    fd_close(dt->fd) ; dt->fd = -1 ;
+    errno = e ;
+    return 0 ;
+  }
+  dt->querylen = 0 ;
+  fd_close(dt->fd) ; dt->fd = -1 ;
+  dt->flagreading = 0 ;
+  return 1 ;
+}
+
+static int s6dns_engine_read_tcp (s6dns_engine_t *dt, tain_t const *stamp)
+{
+  register int r = sanitize_read(mininetstring_read(dt->fd, &dt->sa, &dt->protostate)) ;
+  if (r < 0) return (prepare_next(dt, stamp, 1), 0) ;
+  else if (!r) return (errno = EAGAIN, 0) ;
+  else if ((dt->sa.len - dt->querylen) < 12)
+  {
+    errno = EPROTO ;
+    goto badanswer ;
+  }
+  else
+  {
+    s6dns_message_header_t h ;
+    switch (relevant(dt->sa.s + 2, dt->querylen - 2, dt->sa.s + dt->querylen, dt->sa.len - dt->querylen, dt->flagstrict))
+    {
+      case -1 : if (dt->flagstrict) { dt->sa.len = dt->querylen ; return 0 ; }
+      case 0 : goto badanswer ;
+      case 1 : break ;
+      default : dt->sa.len = dt->querylen ; return (errno = EDOM, 0) ; /* can't happen */
+    }
+    if (dt->debughook && dt->debughook->post_recv) (*dt->debughook->post_recv)(dt, dt->debughook->external) ;
+    s6dns_message_header_unpack(dt->sa.s + dt->querylen, &h) ;
+    if (h.tc) goto badanswer ;
+    switch (h.rcode)
+    {
+      case 0 : case 3 : break ; /* normal operation */
+      case 1 : case 4 : case 5 :
+        byte_zero(s6dns_ip46list_ip(&dt->servers, dt->curserver), SKALIBS_IP_SIZE) ; /* do not query it again */
+      default : goto badanswer ;
+    }
+    fd_close(dt->fd) ; dt->fd = -1 ;
+    dt->flagreading = 0 ;
+    return 1 ;
+  }
+ badanswer:
+  dt->sa.len = dt->querylen ;
+  prepare_next(dt, stamp, 1) ;
+  return 0 ;
+}
+
+
+void s6dns_engine_recycle (s6dns_engine_t *dt)
+{
+  dt->sa.len = 0 ;
+  dt->querylen = 0 ;
+  byte_zero(&dt->servers, sizeof(s6dns_ip46list_t)) ;
+  if (dt->fd >= 0)
+  {
+    register int e = errno ;
+    fd_close(dt->fd) ;
+    dt->fd = -1 ;
+    errno = e ;
+  }
+  dt->status = ECONNABORTED ;
+  dt->flagstrict = dt->flagtcp = dt->flagconnecting = dt->flagreading = dt->flagwriting = 0 ;
+}
+
+int s6dns_engine_timeout (s6dns_engine_t *dt, tain_t const *stamp)
+{
+  if (!error_isagain(dt->status)) return (errno = EINVAL, -1) ;
+  else if (tain_less(&dt->deadline, stamp)) goto yes ;
+  else if (!tain_less(&dt->localdeadline, stamp)) return 0 ;
+  else if (dt->flagwriting) goto yes ;
+  else if (!dt->flagreading) return 0 ;
+  fd_close(dt->fd) ;
+  dt->curserver++ ;
+  if (!s6dns_engine_prepare(dt, stamp, dt->flagtcp))
+  {
+    s6dns_engine_recycle(dt) ;
+    dt->status = errno ;
+    return -1 ;
+  }
+  return 0 ;
+ yes:
+  s6dns_engine_recycle(dt) ;
+  dt->status = ETIMEDOUT ;
+  return 1 ;
+}
+
+int s6dns_engine_event (s6dns_engine_t *dt, tain_t const *stamp)
+{
+  if (!error_isagain(dt->status)) return (errno = EINVAL, -1) ;
+  if (dt->flagwriting)
+    dt->flagtcp ? s6dns_engine_write_tcp(dt, stamp) : s6dns_engine_write_udp(dt, stamp) ;
+  else if (dt->flagreading)
+  {
+    if ((dt->flagtcp) ? s6dns_engine_read_tcp(dt, stamp) : s6dns_engine_read_udp(dt, stamp))
+    {
+      dt->status = 0 ;
+      return 1 ;
+    }
+  }
+  else return (errno = EINVAL, -1) ;
+  if (error_isagain(errno)) return 0 ;
+  s6dns_engine_recycle(dt) ;
+  dt->status = errno ;
+  return -1 ;
+}
+
+int s6dns_engine_init_r (s6dns_engine_t *dt, s6dns_ip46list_t const *servers, uint32 options, char const *q, unsigned int qlen, uint16 qtype, s6dns_debughook_t const *dbh, tain_t const *deadline, tain_t const *stamp)
+{
+  s6dns_message_header_t h = S6DNS_MESSAGE_HEADER_ZERO ;
+  if (!stralloc_ready(&dt->sa, qlen + 18)) return 0 ;
+  dt->deadline = *deadline ;
+  dt->localdeadline = *stamp ;
+  dt->querylen = qlen + 18 ;
+  dt->sa.len = dt->querylen ;
+  dt->servers = *servers ;
+  dt->debughook = dbh ;
+  dt->status = EAGAIN ;
+  dt->flagconnecting = dt->flagreading = dt->flagwriting = 0 ;
+  dt->flagstrict = !!(options & S6DNS_O_STRICT) ;
+  h.rd = !!(options & S6DNS_O_RECURSIVE) ;
+  h.counts.qd = 1 ;
+  uint16_pack_big(dt->sa.s, qlen + 16) ;
+  s6dns_message_header_pack(dt->sa.s + 2, &h) ;
+  byte_copy(dt->sa.s + 14, qlen, q) ;
+  uint16_pack_big(dt->sa.s + 14 + qlen, qtype) ;
+  uint16_pack_big(dt->sa.s + 16 + qlen, S6DNS_C_IN) ;
+  if (qlen > 496) dt->flagtcp = 1 ;
+  else
+  {
+    dt->flagtcp = 0 ;
+    dt->protostate = h.rd ;
+  }
+  if (!s6dns_engine_prepare(dt, stamp, dt->flagtcp))
+  {
+    s6dns_engine_recycle(dt) ;
+    return 0 ;
+  }
+  return 1 ;
+}