[PATCH v2] Enable retrieving of RTNET network packet timestamp OOB using recvmsg()

["François Legal" <devel@thom.fr.eu.org>]

This patch enables retrieving, in realtime application, of RTNET enabled adapters packet timestamps.
It uses the linux semantic SO_TIMESTAMPNS, and the linux code to put the timestamp in the control_msg structure.

I tested this patch with af_packet sockets only. UDP  & TCP might be a little bit trickier as many fragment/segments get reassembled in a single recvmsg. I believe the linux code I used to put the timestamps in the control structure should be OK though.

Signed-off-by: François LEGAL <devel@thom.fr.eu.org>
---
 kernel/drivers/net/stack/Kconfig              |  8 +++
 .../drivers/net/stack/include/rtnet_socket.h  |  7 +++
 kernel/drivers/net/stack/ipv4/tcp/tcp.c       |  8 +++
 kernel/drivers/net/stack/ipv4/udp/udp.c       |  7 +++
 kernel/drivers/net/stack/packet/af_packet.c   |  7 +++
 kernel/drivers/net/stack/socket.c             | 59 +++++++++++++++++++
 6 files changed, 96 insertions(+)

diff --git a/kernel/drivers/net/stack/Kconfig b/kernel/drivers/net/stack/Kconfig
index 830cec5ad..f8ee0f1ad 100644
--- a/kernel/drivers/net/stack/Kconfig
+++ b/kernel/drivers/net/stack/Kconfig
@@ -12,6 +12,14 @@ config XENO_DRIVERS_NET_RX_FIFO_SIZE
     of two! Effectively, only CONFIG_RTNET_RX_FIFO_SIZE-1 slots will
     be usable.

+config XENO_DRIVERS_NET_PACKET_TIMESTAMP
+    bool "Enable packet timestamping (SO_TIMESTAMPNS)"
+    depends on XENO_DRIVERS_NET
+    ---help---
+    Enable userland access to low level packet timestamps using SO_TIMESTAMPNS
+    ioctl on socket. Timestamp are then returned in recvmsg calls in msg_control
+    structure inside msghdr structure.
+
 config XENO_DRIVERS_NET_ETH_P_ALL
     depends on XENO_DRIVERS_NET
     bool "Support for ETH_P_ALL"
diff --git a/kernel/drivers/net/stack/include/rtnet_socket.h b/kernel/drivers/net/stack/include/rtnet_socket.h
index d2caab649..dc488a58a 100644
--- a/kernel/drivers/net/stack/include/rtnet_socket.h
+++ b/kernel/drivers/net/stack/include/rtnet_socket.h
@@ -29,6 +29,7 @@

 #include <asm/atomic.h>
 #include <linux/list.h>
+#include <net/sock.h>

 #include <rtdev.h>
 #include <rtdm/net.h>
@@ -77,6 +78,12 @@ struct rtsocket {
 	} prot;
 };

+#ifdef CONFIG_XENO_DRIVERS_NET_PACKET_TIMESTAMP
+#define SOCKET_FLAG_TIMESTAMP   SOCK_RCVTSTAMPNS
+int rtnet_put_cmsg(struct rtdm_fd *fd, struct user_msghdr *msg, int level,
+					int type, int len, void *data);
+#endif
+
 static inline struct rtdm_fd *rt_socket_fd(struct rtsocket *sock)
 {
 	return rtdm_private_to_fd(sock);
diff --git a/kernel/drivers/net/stack/ipv4/tcp/tcp.c b/kernel/drivers/net/stack/ipv4/tcp/tcp.c
index d8c189c88..c8b21c521 100644
--- a/kernel/drivers/net/stack/ipv4/tcp/tcp.c
+++ b/kernel/drivers/net/stack/ipv4/tcp/tcp.c
@@ -2027,6 +2027,14 @@ static ssize_t rt_tcp_read(struct rtdm_fd *fd, void *buf, size_t nbyte)
 			kfree_rtskb(first_skb); /* or store the data? */
 			return -EFAULT;
 		}
+
+#ifdef CONFIG_XENO_DRIVERS_NET_PACKET_TIMESTAMP
+		if (test_bit(SOCKET_FLAG_TIMESTAMP, &sock->flags))
+			rtnet_put_cmsg(fd, msg, SOL_SOCKET, SCM_TIMESTAMPNS,
+					sizeof(nanosecs_abs_t),
+					(void *) &skb->time_stamp);
+#endif /* CONFIG_XENO_DRIVERS_NET_PACKET_TIMESTAMP */
+
 		rtdm_lock_get_irqsave(&ts->socket_lock, context);
 		if (ts->sync.window) {
 			ts->sync.window += block_size;
diff --git a/kernel/drivers/net/stack/ipv4/udp/udp.c b/kernel/drivers/net/stack/ipv4/udp/udp.c
index 546b35855..ac6448027 100644
--- a/kernel/drivers/net/stack/ipv4/udp/udp.c
+++ b/kernel/drivers/net/stack/ipv4/udp/udp.c
@@ -463,6 +463,13 @@ ssize_t rt_udp_recvmsg(struct rtdm_fd *fd, struct user_msghdr *msg,
 	do {
 		rtskb_trim(skb, data_len);

+#ifdef CONFIG_XENO_DRIVERS_NET_PACKET_TIMESTAMP
+		if (test_bit(SOCKET_FLAG_TIMESTAMP, &sock->flags))
+			rtnet_put_cmsg(fd, msg, SOL_SOCKET, SCM_TIMESTAMPNS,
+					sizeof(nanosecs_abs_t),
+					(void *) &skb->time_stamp);
+#endif /* CONFIG_XENO_DRIVERS_NET_PACKET_TIMESTAMP */
+
 		block_size = skb->len;
 		copied += block_size;
 		data_len -= block_size;
diff --git a/kernel/drivers/net/stack/packet/af_packet.c b/kernel/drivers/net/stack/packet/af_packet.c
index cc7487303..10e8113fe 100644
--- a/kernel/drivers/net/stack/packet/af_packet.c
+++ b/kernel/drivers/net/stack/packet/af_packet.c
@@ -364,6 +364,13 @@ static ssize_t rt_packet_recvmsg(struct rtdm_fd *fd, struct user_msghdr *msg,
 	if (rtdm_fd_to_context(fd)->device->driver->socket_type != SOCK_DGRAM)
 		rtskb_push(rtskb, rtskb->data - rtskb->mac.raw);

+#ifdef CONFIG_XENO_DRIVERS_NET_PACKET_TIMESTAMP
+		if (test_bit(SOCKET_FLAG_TIMESTAMP, &sock->flags))
+			rtnet_put_cmsg(fd, msg, SOL_SOCKET, SCM_TIMESTAMPNS,
+					sizeof(nanosecs_abs_t),
+					(void *) &rtskb->time_stamp);
+#endif /* CONFIG_XENO_DRIVERS_NET_PACKET_TIMESTAMP */
+
 	/* The data must not be longer than the available buffer size */
 	copy_len = rtskb->len;
 	len = rtdm_get_iov_flatlen(iov, msg->msg_iovlen);
diff --git a/kernel/drivers/net/stack/socket.c b/kernel/drivers/net/stack/socket.c
index f030663be..5a9702975 100644
--- a/kernel/drivers/net/stack/socket.c
+++ b/kernel/drivers/net/stack/socket.c
@@ -273,6 +273,15 @@ int rt_socket_if_ioctl(struct rtdm_fd *fd, int request, void __user *arg)
 		return rtnet_put_arg(fd, &u_ifc->ifc_len, &size, sizeof(size));
 	}

+#ifdef CONFIG_XENO_DRIVERS_NET_PACKET_TIMESTAMP
+	if (request == SO_TIMESTAMPNS) {
+		struct rtsocket *sock = rtdm_fd_to_private(fd);
+
+		set_bit(SOCKET_FLAG_TIMESTAMP, &sock->flags);
+		return 0;
+	}
+#endif
+
 	u_ifr = arg;
 	ifr = rtnet_get_arg(fd, &_ifr, u_ifr, sizeof(_ifr));
 	if (IS_ERR(ifr))
@@ -393,3 +402,53 @@ int rtnet_put_arg(struct rtdm_fd *fd, void *dst, const void *src, size_t len)
 	return rtdm_copy_to_user(fd, dst, src, len);
 }
 EXPORT_SYMBOL_GPL(rtnet_put_arg);
+
+#ifdef CONFIG_XENO_DRIVERS_NET_PACKET_TIMESTAMP
+int rtnet_put_cmsg(struct rtdm_fd *fd, struct user_msghdr *msg, int level,
+					int type, int len, void *data)
+{
+	struct cmsghdr __user *cm = msg->msg_control;
+	struct cmsghdr cmhdr;
+	int cmlen = CMSG_LEN(len);
+	int err;
+
+	if (MSG_CMSG_COMPAT & msg->msg_flags)
+		return 0; /* XXX: return error? check spec. */
+
+	if ((cm == NULL) || (msg->msg_controllen < sizeof(*cm))) {
+		msg->msg_flags |= MSG_CTRUNC;
+		return 0; /* XXX: return error? check spec. */
+	}
+	if (msg->msg_controllen < cmlen) {
+		msg->msg_flags |= MSG_CTRUNC;
+		cmlen = msg->msg_controllen;
+	}
+	cmhdr.cmsg_level = level;
+	cmhdr.cmsg_type = type;
+	cmhdr.cmsg_len = cmlen;
+
+	err = -EFAULT;
+
+	if (!rtdm_fd_is_user(fd)) {
+		memcpy(cm, &cmhdr, sizeof(struct cmsghdr));
+		memcpy(CMSG_DATA(cm), data, cmlen - sizeof(struct cmsghdr));
+		err = 0;
+	} else {
+		if (rtdm_copy_to_user(fd, cm, &cmhdr, sizeof(struct cmsghdr)))
+			goto out;
+		if (rtdm_copy_to_user(fd, CMSG_DATA(cm), data,
+					cmlen - sizeof(struct cmsghdr)))
+			goto out;
+		cmlen = CMSG_SPACE(len);
+		if (msg->msg_controllen < cmlen)
+			cmlen = msg->msg_controllen;
+		msg->msg_control += cmlen;
+		msg->msg_controllen -= cmlen;
+		err = 0;
+	}
+out:
+	return err;
+}
+EXPORT_SYMBOL(rtdm_put_cmsg);
+
+#endif /* CONFIG_XENO_DRIVERS_NET_PACKET_TIMESTAMP */
--
2.20.1