MAJOR: listener: support inheriting a listening fd from the parent
Using the address syntax "fd@<num>", a listener may inherit a file
descriptor that the caller process has already bound and passed as
this number. The fd's socket family is detected using getsockname(),
and the usual initialization is performed through the existing code
for that family, but the socket creation is skipped.
Whether the parent has performed the listen() call or not is not
important as this is detected.
For UNIX sockets, we immediately clear the path after preparing a
socket so that we never remove it in case an abort would happen due
to a late error during startup.
diff --git a/src/proto_tcp.c b/src/proto_tcp.c
index 6bd5761..38b9bdc 100644
--- a/src/proto_tcp.c
+++ b/src/proto_tcp.c
@@ -566,6 +566,8 @@
{
__label__ tcp_return, tcp_close_return;
int fd, err;
+ int ext, ready;
+ socklen_t ready_len;
const char *msg = NULL;
/* ensure we never return garbage */
@@ -577,7 +579,15 @@
err = ERR_NONE;
- if ((fd = socket(listener->addr.ss_family, SOCK_STREAM, IPPROTO_TCP)) == -1) {
+ /* if the listener already has an fd assigned, then we were offered the
+ * fd by an external process (most likely the parent), and we don't want
+ * to create a new socket. However we still want to set a few flags on
+ * the socket.
+ */
+ fd = listener->fd;
+ ext = (fd >= 0);
+
+ if (!ext && (fd = socket(listener->addr.ss_family, SOCK_STREAM, IPPROTO_TCP)) == -1) {
err |= ERR_RETRYABLE | ERR_ALERT;
msg = "cannot create listening socket";
goto tcp_return;
@@ -595,7 +605,7 @@
goto tcp_close_return;
}
- if (setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one)) == -1) {
+ if (!ext && setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one)) == -1) {
/* not fatal but should be reported */
msg = "cannot do so_reuseaddr";
err |= ERR_ALERT;
@@ -608,10 +618,11 @@
/* OpenBSD supports this. As it's present in old libc versions of Linux,
* it might return an error that we will silently ignore.
*/
- setsockopt(fd, SOL_SOCKET, SO_REUSEPORT, &one, sizeof(one));
+ if (!ext)
+ setsockopt(fd, SOL_SOCKET, SO_REUSEPORT, &one, sizeof(one));
#endif
#ifdef CONFIG_HAP_LINUX_TPROXY
- if (listener->options & LI_O_FOREIGN) {
+ if (!ext && (listener->options & LI_O_FOREIGN)) {
switch (listener->addr.ss_family) {
case AF_INET:
if ((setsockopt(fd, SOL_IP, IP_TRANSPARENT, &one, sizeof(one)) == -1)
@@ -631,7 +642,7 @@
#endif
#ifdef SO_BINDTODEVICE
/* Note: this might fail if not CAP_NET_RAW */
- if (listener->interface) {
+ if (!ext && listener->interface) {
if (setsockopt(fd, SOL_SOCKET, SO_BINDTODEVICE,
listener->interface, strlen(listener->interface) + 1) == -1) {
msg = "cannot bind listener to device";
@@ -675,13 +686,19 @@
setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, &zero, sizeof(zero));
#endif
- if (bind(fd, (struct sockaddr *)&listener->addr, listener->proto->sock_addrlen) == -1) {
+ if (!ext && bind(fd, (struct sockaddr *)&listener->addr, listener->proto->sock_addrlen) == -1) {
err |= ERR_RETRYABLE | ERR_ALERT;
msg = "cannot bind socket";
goto tcp_close_return;
}
- if (listen(fd, listener->backlog ? listener->backlog : listener->maxconn) == -1) {
+ ready = 0;
+ ready_len = sizeof(ready);
+ if (getsockopt(fd, SOL_SOCKET, SO_ACCEPTCONN, &ready, &ready_len) == -1)
+ ready = 0;
+
+ if (!(ext && ready) && /* only listen if not already done by external process */
+ listen(fd, listener->backlog ? listener->backlog : listener->maxconn) == -1) {
err |= ERR_RETRYABLE | ERR_ALERT;
msg = "cannot listen to socket";
goto tcp_close_return;