sandbox: eth: Add support for using the 'lo' interface

The 'lo' interface on Linux doesn't support thinks like ARP or
link-layer access like we use to talk to a normal network interface.
A higher-level network API must be used to access localhost.

As written, this interface is limited to not supporting ICMP since the
API doesn't allow the socket to be opened for all IP traffic and be able
to receive at the same time. UDP is far more useful to test with, so it
was selected over ICMP. Ping won't work, but things like TFTP should
work.

Signed-off-by: Joe Hershberger <joe.hershberger@ni.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

3 files changed, 127 insertions, 3 deletions

diff --git a/arch/sandbox/cpu/eth-raw-os.c b/arch/sandbox/cpu/eth-raw-os.c
index 601205a..b76a731 100644
--- a/arch/sandbox/cpu/eth-raw-os.c
+++ b/arch/sandbox/cpu/eth-raw-os.c
@@ -12,6 +12,8 @@
 #include <fcntl.h>
 #include <net/if.h>
 #include <netinet/in.h>
+#include <netinet/ip.h>
+#include <netinet/udp.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -20,10 +22,11 @@
 #include <sys/socket.h>
 #include <unistd.h>
 
+#include <arpa/inet.h>
 #include <linux/if_ether.h>
 #include <linux/if_packet.h>
 
-int sandbox_eth_raw_os_start(const char *ifname, unsigned char *ethmac,
+static int _raw_packet_start(const char *ifname, unsigned char *ethmac,
 			    struct eth_sandbox_raw_priv *priv)
 {
 	struct sockaddr_ll *device;
@@ -89,14 +92,114 @@ int sandbox_eth_raw_os_start(const char *ifname, unsigned char *ethmac,
 	return 0;
 }
 
+static int _local_inet_start(struct eth_sandbox_raw_priv *priv)
+{
+	struct sockaddr_in *device;
+	int ret;
+	int flags;
+	int one = 1;
+
+	/* Prepare device struct */
+	priv->device = malloc(sizeof(struct sockaddr_in));
+	if (priv->device == NULL)
+		return -ENOMEM;
+	device = priv->device;
+	memset(device, 0, sizeof(struct sockaddr_in));
+	device->sin_family = AF_INET;
+	device->sin_addr.s_addr = htonl(INADDR_LOOPBACK);
+
+	/**
+	 * Open socket
+	 *  Since we specify UDP here, any incoming ICMP packets will
+	 *  not be received, so things like ping will not work on this
+	 *  localhost interface.
+	 */
+	priv->sd = socket(AF_INET, SOCK_RAW, IPPROTO_UDP);
+	if (priv->sd < 0) {
+		printf("Failed to open socket: %d %s\n", errno,
+		       strerror(errno));
+		return -errno;
+	}
+
+	/* Make the socket non-blocking */
+	flags = fcntl(priv->sd, F_GETFL, 0);
+	fcntl(priv->sd, F_SETFL, flags | O_NONBLOCK);
+
+	/* Include the UDP/IP headers on send and receive */
+	ret = setsockopt(priv->sd, IPPROTO_IP, IP_HDRINCL, &one,
+			 sizeof(one));
+	if (ret < 0) {
+		printf("Failed to set header include option: %d %s\n", errno,
+		       strerror(errno));
+		return -errno;
+	}
+	priv->local_bind_sd = -1;
+	priv->local_bind_udp_port = 0;
+	return 0;
+}
+
+int sandbox_eth_raw_os_start(const char *ifname, unsigned char *ethmac,
+			    struct eth_sandbox_raw_priv *priv)
+{
+	if (priv->local)
+		return _local_inet_start(priv);
+	else
+		return _raw_packet_start(ifname, ethmac, priv);
+}
+
 int sandbox_eth_raw_os_send(void *packet, int length,
-			    const struct eth_sandbox_raw_priv *priv)
+			    struct eth_sandbox_raw_priv *priv)
 {
 	int retval;
+	struct udphdr *udph = packet + sizeof(struct iphdr);
 
 	if (!priv->sd || !priv->device)
 		return -EINVAL;
 
+	/*
+	 * This block of code came about when testing tftp on the localhost
+	 * interface. When using the RAW AF_INET API, the network stack is still
+	 * in play responding to incoming traffic based on open "ports". Since
+	 * it is raw (at the IP layer, no Ethernet) the network stack tells the
+	 * TFTP server that the port it responded to is closed. This causes the
+	 * TFTP transfer to be aborted. This block of code inspects the outgoing
+	 * packet as formulated by the u-boot network stack to determine the
+	 * source port (that the TFTP server will send packets back to) and
+	 * opens a typical UDP socket on that port, thus preventing the network
+	 * stack from sending that ICMP message claiming that the port has no
+	 * bound socket.
+	 */
+	if (priv->local && (priv->local_bind_sd == -1 ||
+			    priv->local_bind_udp_port != udph->source)) {
+		struct iphdr *iph = packet;
+		struct sockaddr_in addr;
+
+		if (priv->local_bind_sd != -1)
+			close(priv->local_bind_sd);
+
+		/* A normal UDP socket is required to bind */
+		priv->local_bind_sd = socket(AF_INET, SOCK_DGRAM, 0);
+		if (priv->local_bind_sd < 0) {
+			printf("Failed to open bind sd: %d %s\n", errno,
+			       strerror(errno));
+			return -errno;
+		}
+		priv->local_bind_udp_port = udph->source;
+
+		/**
+		 * Bind the UDP port that we intend to use as our source port
+		 * so that the kernel will not send an ICMP port unreachable
+		 * message to the server
+		 */
+		addr.sin_family = AF_INET;
+		addr.sin_port = udph->source;
+		addr.sin_addr.s_addr = iph->saddr;
+		retval = bind(priv->local_bind_sd, &addr, sizeof(addr));
+		if (retval < 0)
+			printf("Failed to bind: %d %s\n", errno,
+			       strerror(errno));
+	}
+
 	retval = sendto(priv->sd, packet, length, 0,
 			(struct sockaddr *)priv->device,
 			sizeof(struct sockaddr_ll));
@@ -137,4 +240,10 @@ void sandbox_eth_raw_os_stop(struct eth_sandbox_raw_priv *priv)
 	priv->device = NULL;
 	close(priv->sd);
 	priv->sd = -1;
+	if (priv->local) {
+		if (priv->local_bind_sd != -1)
+			close(priv->local_bind_sd);
+		priv->local_bind_sd = -1;
+		priv->local_bind_udp_port = 0;
+	}
 }
diff --git a/arch/sandbox/dts/sandbox.dts b/arch/sandbox/dts/sandbox.dts
index 553bfbe..7d050d9 100644
--- a/arch/sandbox/dts/sandbox.dts
+++ b/arch/sandbox/dts/sandbox.dts
@@ -5,6 +5,7 @@
 	#size-cells = <1>;
 
 	aliases {
+		eth5 = "/eth@90000000";
 		pci0 = &pci;
 	};
 
@@ -212,4 +213,10 @@
 		reg = <0x80000000 0x1000>;
 		host-raw-interface = "eth0";
 	};
+
+	eth@90000000 {
+		compatible = "sandbox,eth-raw";
+		reg = <0x90000000 0x1000>;
+		host-raw-interface = "lo";
+	};
 };
diff --git a/arch/sandbox/include/asm/eth-raw-os.h b/arch/sandbox/include/asm/eth-raw-os.h
index df60c4f..ed4b2e2 100644
--- a/arch/sandbox/include/asm/eth-raw-os.h
+++ b/arch/sandbox/include/asm/eth-raw-os.h
@@ -15,16 +15,24 @@
  *
  * sd: socket descriptor - the open socket during a session
  * device: struct sockaddr_ll - the host interface packets move to/from
+ * local: 1 or 0 to select the local interface ('lo') or not
+ * local_bindsd: socket descriptor to prevent the kernel from sending
+ *		 a message to the server claiming the port is
+ *		 unreachable
+ * local_bind_udp_port: The UDP port number that we bound to
  */
 struct eth_sandbox_raw_priv {
 	int sd;
 	void *device;
+	int local;
+	int local_bind_sd;
+	unsigned short local_bind_udp_port;
 };
 
 int sandbox_eth_raw_os_start(const char *ifname, unsigned char *ethmac,
 			    struct eth_sandbox_raw_priv *priv);
 int sandbox_eth_raw_os_send(void *packet, int length,
-			    const struct eth_sandbox_raw_priv *priv);
+			    struct eth_sandbox_raw_priv *priv);
 int sandbox_eth_raw_os_recv(void *packet, int *length,
 			    const struct eth_sandbox_raw_priv *priv);
 void sandbox_eth_raw_os_stop(struct eth_sandbox_raw_priv *priv);