Menu
▾
▴
[commit] master: make DNS lookup asynchronous
|
From: Oswald B. <os...@us...> - 2022-07-04 16:29:56
|
commit ec50c55c36887b86b0143a265acae4b22d117fe9
Author: Oswald Buddenhagen <os...@us...>
Date: Mon Jul 4 12:50:17 2022 +0200
make DNS lookup asynchronous
true asynchronicity is actually fairly useless, as it's unlikely that
both Stores in a Channel use IMAP, and both host resolutions take
particularly long - the main objective is imposing the Timeout setting.
however, we can't just use setjmp()+alarm(), as longjmp()ing out of
getaddrinfo() is undefined, as it may for example free() just at the
wrong time. so we go for the real thing.
this implementation just fork()s out a process which uses getaddrinfo()
(or gethostbyname()) per lookup. this isn't particularly scalable, but
as we don't expect a lot of lookups, it seems adequate.
src/socket.c | 281 +++++++++++++++++++++++++++++++++++----------------
src/socket.h | 6 +-
2 files changed, 195 insertions(+), 92 deletions(-)
diff --git a/src/socket.c b/src/socket.c
index 8f41295..52cd7c2 100644
--- a/src/socket.c
+++ b/src/socket.c
@@ -28,6 +28,7 @@
#endif
enum {
+ SCK_RESOLVING,
SCK_CONNECTING,
#ifdef HAVE_LIBSSL
SCK_STARTTLS,
@@ -415,6 +416,7 @@ static void socket_fd_cb( int, void * );
static void socket_fake_cb( void * );
static void socket_timeout_cb( void * );
+static void socket_resolve( conn_t * );
static void socket_connect_one( conn_t * );
static void socket_connect_next( conn_t * );
static void socket_connect_failed( conn_t * );
@@ -422,15 +424,21 @@ static void socket_connected( conn_t * );
static void socket_connect_bail( conn_t * );
static void
-socket_open_internal( conn_t *sock, int fd )
+socket_register_internal( conn_t *sock, int fd )
{
sock->fd = fd;
- fcntl( fd, F_SETFL, O_NONBLOCK );
init_notifier( &sock->notify, fd, socket_fd_cb, sock );
init_wakeup( &sock->fd_fake, socket_fake_cb, sock );
init_wakeup( &sock->fd_timeout, socket_timeout_cb, sock );
}
+static void
+socket_open_internal( conn_t *sock, int fd )
+{
+ fcntl( fd, F_SETFL, O_NONBLOCK );
+ socket_register_internal( sock, fd );
+}
+
static void
socket_close_internal( conn_t *sock )
{
@@ -441,32 +449,6 @@ socket_close_internal( conn_t *sock )
sock->fd = -1;
}
-#ifndef HAVE_IPV6
-struct addr_info {
- struct addr_info *ai_next;
- struct sockaddr_in ai_addr[1];
-};
-
-#define freeaddrinfo(ai) free( ai )
-
-static struct addr_info *
-init_addrinfo( struct hostent *he )
-{
- uint naddr = 0;
- for (char **addr = he->h_addr_list; *addr; addr++)
- naddr++;
- struct addr_info *caddr = nfzalloc( naddr * sizeof(struct addrinfo) );
- struct addr_info *ret, **caddrp = &ret;
- for (char **addr = he->h_addr_list; *addr; addr++, caddr++) {
- caddr->ai_addr->sin_family = AF_INET;
- memcpy( &caddr->ai_addr->sin_addr.s_addr, *addr, sizeof(struct in_addr) );
- *caddrp = caddr;
- caddrp = &caddr->ai_next;
- }
- return ret;
-}
-#endif
-
void
socket_connect( conn_t *sock, void (*cb)( int ok, void *aux ) )
{
@@ -501,77 +483,202 @@ socket_connect( conn_t *sock, void (*cb)( int ok, void *aux ) )
info( "\vok\n" );
socket_connected( sock );
} else {
+ socket_resolve( sock );
+ }
+}
+
+static void
+pipe_write( int fd, void *buf, int len )
+{
+ do {
+ int wrote = write( fd, buf, len );
+ if (wrote < 0) {
+ perror( "write" );
+ _exit( 1 );
+ }
+ buf = ((char *)buf) + wrote;
+ len -= wrote;
+ } while (len);
+}
+
+static void
+socket_resolve( conn_t *sock )
+{
+ info( "Resolving %s...\n", sock->conf->host );
+
+ int pfd[2];
+ if (pipe( pfd )) {
+ perror( "pipe" );
+ exit( 1 );
+ }
+ switch (fork()) {
+ case -1:
+ perror( "fork" );
+ exit( 1 );
+ case 0:
+ break;
+ default:
+ close( pfd[1] );
+ socket_register_internal( sock, pfd[0] );
+ sock->state = SCK_RESOLVING;
+ conf_notifier( &sock->notify, 0, POLLIN );
+ socket_expect_activity( sock, 1 );
+ return;
+ }
+
#ifdef HAVE_IPV6
- int gaierr;
- struct addrinfo hints;
-
- memset( &hints, 0, sizeof(hints) );
- hints.ai_family = AF_UNSPEC;
- hints.ai_socktype = SOCK_STREAM;
- hints.ai_flags = AI_ADDRCONFIG;
- infon( "Resolving %s... ", conf->host );
- if ((gaierr = getaddrinfo( conf->host, NULL, &hints, &sock->addrs ))) {
- error( "Error: Cannot resolve server '%s': %s\n", conf->host, gai_strerror( gaierr ) );
- socket_connect_bail( sock );
- return;
+ struct addrinfo *res, hints = { 0 };
+ hints.ai_family = AF_UNSPEC;
+ hints.ai_socktype = SOCK_STREAM;
+ hints.ai_flags = AI_ADDRCONFIG;
+ int gaierr = getaddrinfo( sock->conf->host, NULL, &hints, &res );
+ pipe_write( pfd[1], &gaierr, sizeof(gaierr) );
+ if (gaierr)
+ _exit( 1 );
+ static_assert( sizeof(((struct addrinfo){ 0 }).ai_family) == sizeof(int), "unexpected size of ai_family" );
+ static_assert( sizeof(struct in_addr) % sizeof(int) == 0, "unexpected size of struct in_addr" );
+ static_assert( sizeof(struct in6_addr) % sizeof(int) == 0, "unexpected size of struct in6_addr" );
+ int nbytes = 0;
+ for (struct addrinfo *cres = res; cres; cres = cres->ai_next) {
+ if (cres->ai_family == AF_INET) {
+ nbytes += sizeof(int) + sizeof(struct in_addr);
+ } else {
+ assert( cres->ai_family == AF_INET6 );
+ nbytes += sizeof(int) + sizeof(struct in6_addr);
}
- info( "\vok\n" );
+ }
+ pipe_write( pfd[1], &nbytes, sizeof(nbytes) );
+ for (struct addrinfo *cres = res; cres; cres = cres->ai_next) {
+ pipe_write( pfd[1], &cres->ai_family, sizeof(int) );
+ if (cres->ai_family == AF_INET)
+ pipe_write( pfd[1], &((struct sockaddr_in *)cres->ai_addr)->sin_addr, sizeof(struct in_addr) );
+ else
+ pipe_write( pfd[1], &((struct sockaddr_in6 *)cres->ai_addr)->sin6_addr, sizeof(struct in6_addr) );
+ }
#else
- struct hostent *he;
+ struct hostent *he = gethostbyname( sock->conf->host );
+ int herrno = he ? 0 : h_errno;
+ pipe_write( pfd[1], &herrno, sizeof(herrno) );
+ if (!he)
+ _exit( 1 );
+ static_assert( sizeof(struct in_addr) % sizeof(int) == 0, "unexpected size of struct in_addr" );
+ int nbytes = 0;
+ for (char **addr = he->h_addr_list; *addr; addr++)
+ nbytes += sizeof(struct in_addr);
+ pipe_write( pfd[1], &nbytes, sizeof(nbytes) );
+ for (char **addr = he->h_addr_list; *addr; addr++)
+ pipe_write( pfd[1], *addr, sizeof(struct in_addr) );
+#endif
+ _exit( 0 );
+}
- infon( "Resolving %s... ", conf->host );
- he = gethostbyname( conf->host );
- if (!he) {
- error( "Error: Cannot resolve server '%s': %s\n", conf->host, hstrerror( h_errno ) );
- socket_connect_bail( sock );
- return;
+static void
+pipe_read( int fd, void *buf, int len )
+{
+ do {
+ int didrd = read( fd, buf, len );
+ if (didrd < 0) {
+ sys_error( "read" );
+ exit( 1 );
}
- info( "\vok\n" );
-
- sock->addrs = init_addrinfo( he );
-#endif
- sock->curr_addr = sock->addrs;
- socket_connect_one( sock );
- }
+ if (!didrd) {
+ error( "read: unexpected EOF\n" );
+ exit( 1 );
+ }
+ buf = ((char *)buf) + didrd;
+ len -= didrd;
+ } while (len);
}
static void
-socket_connect_one( conn_t *sock )
+socket_resolve_finalize( conn_t *sock )
{
- int s;
+ int errcode;
+ pipe_read( sock->fd, &errcode, sizeof(errcode) );
+ if (errcode) {
#ifdef HAVE_IPV6
- struct addrinfo *ai;
+ const char *err = gai_strerror( errcode );
#else
- struct addr_info *ai;
+ const char *err = hstrerror( errcode );
#endif
+ error( "Error: Cannot resolve server '%s': %s\n", sock->conf->host, err );
+ socket_close_internal( sock );
+ socket_connect_bail( sock );
+ return;
+ }
- if (!(ai = sock->curr_addr)) {
+ int nbytes;
+ pipe_read( sock->fd, &nbytes, sizeof(nbytes) );
+ char *addrs = nfmalloc( nbytes );
+ pipe_read( sock->fd, addrs, nbytes );
+ sock->curr_addr = sock->addrs = addrs;
+ sock->addrs_end = addrs + nbytes;
+ socket_close_internal( sock ); // Get rid of the pipe
+ socket_connect_one( sock );
+}
+
+static void
+socket_resolve_timeout( conn_t *sock )
+{
+ error( "Error: Cannot resolve server '%s': timeout.\n", sock->conf->host );
+ socket_close_internal( sock );
+ socket_connect_bail( sock );
+}
+
+static void
+socket_connect_one( conn_t *sock )
+{
+ char *ai = sock->curr_addr;
+ if (ai == sock->addrs_end) {
error( "No working address found for %s\n", sock->conf->host );
socket_connect_bail( sock );
return;
}
+ union {
+ struct sockaddr any;
+ struct sockaddr_in ip4;
+#ifdef HAVE_IPV6
+ struct sockaddr_in6 ip6;
+#endif
+ } addr;
+
+#ifdef HAVE_IPV6
+ int fam = *(int *)ai;
+ ai += sizeof(int);
+ int addr_len;
+ if (fam == AF_INET6) {
+ addr_len = sizeof(addr.ip6);
+ addr.ip6.sin6_addr = *(struct in6_addr *)ai;
+ addr.ip6.sin6_flowinfo = 0;
+ addr.ip6.sin6_scope_id = 0;
+ ai += sizeof(struct in6_addr);
+ } else {
+ addr_len = sizeof(addr.ip4);
+#else
+ const int fam = AF_INET;
+ const int addr_len = sizeof(addr.ip4);
+ {
+#endif
+ addr.ip4.sin_addr = *(struct in_addr *)ai;
+ ai += sizeof(struct in_addr);
+ }
+ sock->curr_addr = ai;
+
#ifdef HAVE_IPV6
- if (ai->ai_family == AF_INET6) {
- struct sockaddr_in6 *in6 = ((struct sockaddr_in6 *)ai->ai_addr);
+ if (fam == AF_INET6) {
char sockname[64];
- in6->sin6_port = htons( sock->conf->port );
+ inet_ntop( fam, &addr.ip6.sin6_addr, sockname, sizeof(sockname) );
nfasprintf( &sock->name, "%s ([%s]:%hu)",
- sock->conf->host, inet_ntop( AF_INET6, &in6->sin6_addr, sockname, sizeof(sockname) ), sock->conf->port );
+ sock->conf->host, sockname, sock->conf->port );
} else
#endif
{
- struct sockaddr_in *in = ((struct sockaddr_in *)ai->ai_addr);
- in->sin_port = htons( sock->conf->port );
nfasprintf( &sock->name, "%s (%s:%hu)",
- sock->conf->host, inet_ntoa( in->sin_addr ), sock->conf->port );
+ sock->conf->host, inet_ntoa( addr.ip4.sin_addr ), sock->conf->port );
}
-#ifdef HAVE_IPV6
- s = socket( ai->ai_family, SOCK_STREAM, 0 );
-#else
- s = socket( PF_INET, SOCK_STREAM, 0 );
-#endif
+ int s = socket( fam, SOCK_STREAM, 0 );
if (s < 0) {
socket_connect_next( sock );
return;
@@ -579,11 +686,9 @@ socket_connect_one( conn_t *sock )
socket_open_internal( sock, s );
infon( "Connecting to %s... ", sock->name );
-#ifdef HAVE_IPV6
- if (connect( s, ai->ai_addr, ai->ai_addrlen )) {
-#else
- if (connect( s, ai->ai_addr, sizeof(*ai->ai_addr) )) {
-#endif
+ addr.any.sa_family = fam;
+ addr.ip4.sin_port = htons( sock->conf->port ); // Aliased for ip6
+ if (connect( s, &addr.any, addr_len )) {
if (errno != EINPROGRESS) {
socket_connect_failed( sock );
return;
@@ -604,7 +709,6 @@ socket_connect_next( conn_t *conn )
sys_error( "Cannot connect to %s", conn->name );
free( conn->name );
conn->name = NULL;
- conn->curr_addr = conn->curr_addr->ai_next;
socket_connect_one( conn );
}
@@ -618,10 +722,8 @@ socket_connect_failed( conn_t *conn )
static void
socket_connected( conn_t *conn )
{
- if (conn->addrs) {
- freeaddrinfo( conn->addrs );
- conn->addrs = NULL;
- }
+ free( conn->addrs );
+ conn->addrs = NULL;
conf_notifier( &conn->notify, 0, POLLIN );
socket_expect_activity( conn, 0 );
conn->state = SCK_READY;
@@ -631,10 +733,8 @@ socket_connected( conn_t *conn )
static void
socket_cleanup_names( conn_t *conn )
{
- if (conn->addrs) {
- freeaddrinfo( conn->addrs );
- conn->addrs = NULL;
- }
+ free( conn->addrs );
+ conn->addrs = NULL;
free( conn->name );
conn->name = NULL;
}
@@ -1106,6 +1206,11 @@ socket_fd_cb( int events, void *aux )
{
conn_t *conn = (conn_t *)aux;
+ if (conn->state == SCK_RESOLVING) {
+ socket_resolve_finalize( conn );
+ return;
+ }
+
if ((events & POLLERR) || conn->state == SCK_CONNECTING) {
int soerr;
socklen_t selen = sizeof(soerr);
@@ -1168,7 +1273,9 @@ socket_timeout_cb( void *aux )
{
conn_t *conn = (conn_t *)aux;
- if (conn->state == SCK_CONNECTING) {
+ if (conn->state == SCK_RESOLVING) {
+ socket_resolve_timeout( conn );
+ } else if (conn->state == SCK_CONNECTING) {
errno = ETIMEDOUT;
socket_connect_failed( conn );
} else {
diff --git a/src/socket.h b/src/socket.h
index 0e40f48..5b538eb 100644
--- a/src/socket.h
+++ b/src/socket.h
@@ -57,11 +57,7 @@ typedef struct {
int fd;
int state;
const server_conf_t *conf; /* needed during connect */
-#ifdef HAVE_IPV6
- struct addrinfo *addrs, *curr_addr; /* needed during connect */
-#else
- struct addr_info *addrs, *curr_addr; /* needed during connect */
-#endif
+ char *addrs, *addrs_end, *curr_addr; // needed during connect; assumed to be int-aligned
char *name;
#ifdef HAVE_LIBSSL
SSL *ssl;
|
