From 415a6a1ced90cc8b8691eb7ab027bba4611fc236 Mon Sep 17 00:00:00 2001

From: Stefan Hajnoczi <stefanha@redhat.com>

Date: Wed, 2 Jun 2021 15:51:02 -0400

Subject: [PATCH 04/21] sockets: update SOCKET_ADDRESS_TYPE_FD listen(2)

 backlog

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RH-Author: Miroslav Rezanina <mrezanin@redhat.com>

RH-MergeRequest: 8: Synchronize with RHEL-AV 8.5 release 19 to RHEL 9

RH-Commit: [3/8] a8fd97eb477ad51fca75c1cc344185e1de59caf1 (mrezanin/centos-src-qemu-kvm)

RH-Bugzilla: 1957194

RH-Acked-by: Daniel P. Berrangé <berrange@redhat.com>

RH-Acked-by: Greg Kurz <gkurz@redhat.com>

RH-Acked-by: Laurent Vivier <lvivier@redhat.com>

RH-Acked-by: Vitaly Kuznetsov <vkuznets@redhat.com>

socket_get_fd() fails with the error "socket_get_fd: too many

connections" if the given listen backlog value is not 1.

Not all callers set the backlog to 1. For example, commit

582d4210eb2f2ab5baac328fe4b479cd86da1647 ("qemu-nbd: Use SOMAXCONN for

socket listen() backlog") uses SOMAXCONN. This will always fail with in

socket_get_fd().

This patch calls listen(2) on the fd to update the backlog value. The

socket may already be in the listen state. I have tested that this works

on Linux 5.10 and macOS Catalina.

As a bonus this allows us to detect when the fd cannot listen. Now we'll

be able to catch unbound or connected fds in socket_listen().

Drop the num argument from socket_get_fd() since this function is also

called by socket_connect() where a listen backlog value does not make

sense.

Fixes: e5b6353cf25c99c3f08bf51e29933352f7140e8f ("socket: Add backlog parameter to socket_listen")

Reported-by: Richard W.M. Jones <rjones@redhat.com>

Cc: Juan Quintela <quintela@redhat.com>

Cc: Eric Blake <eblake@redhat.com>

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

Message-Id: <20210310173004.420190-1-stefanha@redhat.com>

Tested-by: Richard W.M. Jones <rjones@redhat.com>

Reviewed-by: Eric Blake <eblake@redhat.com>

Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>

Signed-off-by: Eric Blake <eblake@redhat.com>

(cherry picked from commit 37179e9ea45d6428b29ae789209c119ac18c1d39)

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>

Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>

---

 util/qemu-sockets.c | 29 ++++++++++++++++++++++-------

 1 file changed, 22 insertions(+), 7 deletions(-)

diff --git a/util/qemu-sockets.c b/util/qemu-sockets.c

index 8af0278f15..2463c49773 100644

--- a/util/qemu-sockets.c

+++ b/util/qemu-sockets.c

@@ -1116,14 +1116,10 @@ fail:

     return NULL;

 }

-static int socket_get_fd(const char *fdstr, int num, Error **errp)

+static int socket_get_fd(const char *fdstr, Error **errp)

 {

     Monitor *cur_mon = monitor_cur();

     int fd;

-    if (num != 1) {

-        error_setg_errno(errp, EINVAL, "socket_get_fd: too many connections");

-        return -1;

-    }

     if (cur_mon) {

         fd = monitor_get_fd(cur_mon, fdstr, errp);

         if (fd < 0) {

@@ -1159,7 +1155,7 @@ int socket_connect(SocketAddress *addr, Error **errp)

         break;

     case SOCKET_ADDRESS_TYPE_FD:

-        fd = socket_get_fd(addr->u.fd.str, 1, errp);

+        fd = socket_get_fd(addr->u.fd.str, errp);

         break;

     case SOCKET_ADDRESS_TYPE_VSOCK:

@@ -1187,7 +1183,26 @@ int socket_listen(SocketAddress *addr, int num, Error **errp)

         break;

     case SOCKET_ADDRESS_TYPE_FD:

-        fd = socket_get_fd(addr->u.fd.str, num, errp);

+        fd = socket_get_fd(addr->u.fd.str, errp);

+        if (fd < 0) {

+            return -1;

+        }

+

+        /*

+         * If the socket is not yet in the listen state, then transition it to

+         * the listen state now.

+         *

+         * If it's already listening then this updates the backlog value as

+         * requested.

+         *

+         * If this socket cannot listen because it's already in another state

+         * (e.g. unbound or connected) then we'll catch the error here.

+         */

+        if (listen(fd, num) != 0) {

+            error_setg_errno(errp, errno, "Failed to listen on fd socket");

+            closesocket(fd);

+            return -1;

+        }

         break;

     case SOCKET_ADDRESS_TYPE_VSOCK:

-- 

2.27.0