[Qemu-devel] [PATCH] socket: fix blocking udp recvfrom.

[llyzs]

Sometimes sorecvfrom() is called from slirp.c because revents == G_IO_IN,
however inside sorecvfrom() function, ioctlsocket() returns 0 bytes available
and recvfrom could be blocking indefinitely. This adds a non-blocking flag to
recvfrom and checks data availability.
---
 slirp/socket.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/slirp/socket.c b/slirp/socket.c
index c01d8696af..ea30478ce6 100644
--- a/slirp/socket.c
+++ b/slirp/socket.c
@@ -581,7 +581,7 @@ sorecvfrom(struct socket *so)
          }
          /* } */

-         m->m_len = recvfrom(so->s, m->m_data, len, 0,
+         m->m_len = recvfrom(so->s, m->m_data, len, MSG_DONTWAIT,
                              (struct sockaddr *)&addr, &addrlen);
          DEBUG_MISC((dfd, " did recvfrom %d, errno = %d-%s\n",
                      m->m_len, errno,strerror(errno)));
@@ -618,6 +618,8 @@ sorecvfrom(struct socket *so)
              break;
            }
            m_free(m);
+         } else if (m->m_len==0) {
+           m_free(m);
          } else {
          /*
           * Hack: domain name lookup will be used the most for UDP,
-- 
2.20.1