[U-Boot] [PATCH] Add simple IP/UDP fragmentation support

[Josh Boyer <jwboyer@linux.vnet.ibm.com>]

From: Frank Haverkamp <haver@vnet.ibm.com>

http://tools.ietf.org/html/rfc2348 describes the TFTP block size option
which allows larger packtes than the 512 byte default. This reduces the
number of TFTP ACKs significantly and improves performance.

To get the most benefit out of the tftp block size option the support
of defragementation of IP/UDP packet is helpful. The current implemenation
should work even with packets received out of order. To enable the large
packet size the user should set "tftp_block_size" so a value like 16352.

We experimented with different packet sizes and found that more than those
16KiB do not contribute much to the performance anymore. Therefor I limited
the defragmentation buffer to 16KiB no too waste memory.

Signed-off-by: Frank Haverkamp <haver@vnet.ibm.com>
Signed-off-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>

---
 include/net.h |   17 ++++++
 net/net.c     |  156 ++++++++++++++++++++++++++++++++++++++++++++++++++--------
 net/tftp.c    |   22 ++++++++
 net/tftp.h    |   10 +++
 4 files changed, 185 insertions(+), 20 deletions(-)

--- u-boot.git.orig/include/net.h
+++ u-boot.git/include/net.h
@@ -200,6 +200,13 @@ typedef struct {
 	ushort		udp_xsum;	/* Checksum			*/
 } IP_t;
 
+#define IP_OFFS			 0x1FFF	/* ip offset *= 8 */
+#define	  IP_OFFS_SHIFT	  3	/* in 8 byte steps */
+#define IP_FLAGS	 0xE000	/* first 3 bits */
+#define		 IP_FLAGS_RES	 0x8000	/* reserved */
+#define		 IP_FLAGS_DFRAG	 0x4000	/* don't fragments */
+#define		 IP_FLAGS_MFRAG	 0x2000	/* more fragments */
+
 #define IP_HDR_SIZE_NO_UDP	(sizeof (IP_t) - 8)
 #define IP_HDR_SIZE		(sizeof (IP_t))
 
@@ -282,6 +289,16 @@ typedef struct icmphdr {
 #define PKTSIZE_ALIGN		1536
 /*#define PKTSIZE		608*/
 
+ /*
+  * IP/UDP Fragmentation support
+  * See: http://en.wikipedia.org/wiki/IPv4#Fragmentation_and_reassembly
+  * MAX possible UDP packet size is 64 KiB, if there is memory available.
+  */
+#define NET_ETH_MTU		1500
+#define NET_FRAG_BUF_SIZE	(16 * 1024) /* MAX is 64 KiB */
+#define NET_UDP_FRAG_SIZE	(NET_ETH_MTU - IP_HDR_SIZE_NO_UDP) /* 1480 */
+#define NET_FRAG_BUF_USED	(NET_FRAG_BUF_SIZE / NET_UDP_FRAG_SIZE + 1)
+
 /*
  * Maximum receive ring size; that is, the number of packets
  * we can buffer before overflow happens. Basically, this just
--- u-boot.git.orig/net/net.c
+++ u-boot.git/net/net.c
@@ -192,6 +192,15 @@ volatile uchar	PktBuf[(PKTBUFSRX+1) * PK
 
 volatile uchar *NetRxPackets[PKTBUFSRX]; /* Receive packets			*/
 
+/* Packet fragmentation support */
+static uint16_t ip_id = 0; /* sequence number */
+static uint16_t udp_len = 0;
+static uint16_t udp_src = 0;
+static uint16_t udp_dst = 0;
+static int max_idx = 0;
+static uchar NetFragBuf[NET_FRAG_BUF_SIZE];
+static char NetFragBufUsed[NET_FRAG_BUF_USED] = { 0, };
+
 static rxhand_f *packetHandler;		/* Current RX packet handler		*/
 static thand_f *timeHandler;		/* Current timeout handler		*/
 static ulong	timeStart;		/* Time base value			*/
@@ -288,6 +297,13 @@ NetLoop(proto_t protocol)
 {
 	bd_t *bd = gd->bd;
 
+	/* Packet fragmentation support */
+	ip_id = udp_len = udp_src = udp_dst = max_idx = 0;
+	memset(NetFragBuf, 0xFF, sizeof(NetFragBuf));
+	memset(NetFragBufUsed, 0, sizeof(NetFragBufUsed));
+	printf("NetFragBuf @ %08x max tftp_block_size=%d udp_frag_size=%d\n",
+	       NetFragBuf, TFTP_BLOCK_SIZE_MAX, NET_UDP_FRAG_SIZE);
+
 #ifdef CONFIG_NET_MULTI
 	NetRestarted = 0;
 	NetDevExists = 0;
@@ -1150,6 +1166,39 @@ static void CDPStart(void)
 }
 #endif
 
+#ifdef CONFIG_UDP_CHECKSUM
+/*
+ * @sumptr: Points to UDP data
+ * @sumlen: Size of UDP data
+ * @xsum: UDP checksum across IP source, destination address, protocol and size
+ *
+ * Returns 0 when checksum is correct and 1 if it is not.
+ */
+static int udp_checksum(ushort *sumptr, ushort sumlen, ulong xsum)
+{
+       while (sumlen > 1) {
+	       ushort sumdata;
+
+	       sumdata = *sumptr++;
+	       xsum += ntohs(sumdata);
+	       sumlen -= 2;
+       }
+       if (sumlen > 0) {
+	       ushort sumdata;
+
+	       sumdata = *(unsigned char *) sumptr;
+	       sumdata = (sumdata << 8) & 0xff00;
+	       xsum += sumdata;
+       }
+       while ((xsum >> 16) != 0) {
+	       xsum = (xsum & 0x0000ffff) + ((xsum >> 16) & 0x0000ffff);
+       }
+       if ((xsum != 0x00000000) && (xsum != 0x0000ffff))
+	       return 1;
+
+       return 0;
+}
+#endif /* CONFIG_UDP_CHECKSUM */
 
 void
 NetReceive(volatile uchar * inpkt, int len)
@@ -1164,6 +1213,7 @@ NetReceive(volatile uchar * inpkt, int l
 	int iscdp;
 #endif
 	ushort cti = 0, vlanid = VLAN_NONE, myvlanid, mynvlanid;
+	uint32_t off;		/* ip_off for fragmentation */
 
 #ifdef ET_DEBUG
 	printf("packet received\n");
@@ -1404,9 +1454,11 @@ NetReceive(volatile uchar * inpkt, int l
 		if ((ip->ip_hl_v & 0xf0) != 0x40) {
 			return;
 		}
+#if 0		/* Obsolete after adding the fragmentation support */
 		if (ip->ip_off & htons(0x1fff)) { /* Can't deal w/ fragments */
 			return;
 		}
+#endif
 		/* can't deal with headers > 20 bytes */
 		if ((ip->ip_hl_v & 0x0f) > 0x05) {
 			return;
@@ -1422,6 +1474,88 @@ NetReceive(volatile uchar * inpkt, int l
 #endif
 			return;
 		}
+
+		/*
+		 * Fragmentation support. We need to check the ip_id
+		 * and if all fragments were received correctly.
+		 */
+		off = (ntohs(ip->ip_off) & IP_OFFS) << IP_OFFS_SHIFT;
+		if ((off != 0) || (ip->ip_off & htons(IP_FLAGS_MFRAG))) {
+			int size, idx, complete;
+			char *start;
+
+			/* New fragmented packet arrived, clear data. */
+			if (ntohs(ip->ip_id) != ip_id) {
+				ip_id = ntohs(ip->ip_id);
+				memset(NetFragBufUsed, 0, sizeof(NetFragBufUsed));
+				udp_len = udp_src = udp_dst = max_idx = 0;
+			}
+
+			idx = off / NET_UDP_FRAG_SIZE;
+
+			/* Packet does not fit into IP/UDP fragmentation buf */
+			if (idx >= NET_FRAG_BUF_USED) {
+				return;
+			}
+
+			NetFragBufUsed[idx] = 1;
+
+			/* Copy the UDP hdr with the data for 1st
+			   fragment, else copy just payload */
+			if (off == 0) {
+				udp_len = ntohs(ip->udp_len);
+				udp_src = ntohs(ip->udp_src);
+				udp_dst = ntohs(ip->udp_dst);
+			}
+			size = ntohs(ip->ip_len) - IP_HDR_SIZE_NO_UDP;
+			start = (char *)ip + IP_HDR_SIZE_NO_UDP;
+			memcpy(NetFragBuf + off, start, size);
+
+			/*
+			 * When last fragement has been received we
+			 * know the number of fragments we expect. If
+			 * all have arrived we process the packet.
+			 */
+			if (((off != 0) && !(ip->ip_off & htons(IP_FLAGS_MFRAG))))
+				max_idx = idx;
+
+			if (max_idx == 0)
+				return;
+
+			complete = 1;
+			for (idx = 0; idx < max_idx; idx++) {
+				if (NetFragBufUsed[idx] == 0) {
+					complete = 0;
+					break;
+				}
+			}
+			if (!complete)
+				return;
+#ifdef CONFIG_UDP_CHECKSUM
+			if (ip->udp_xsum != 0) {
+				ulong xsum = ip->ip_p;
+				uint16_t *sumptr;
+
+				xsum += udp_len;
+				xsum += (ntohl(ip->ip_src) >> 16) & 0xffff;
+				xsum += (ntohl(ip->ip_src) >>  0) & 0xffff;
+				xsum += (ntohl(ip->ip_dst) >> 16) & 0xffff;
+				xsum += (ntohl(ip->ip_dst) >>  0) & 0xffff;
+				sumptr = (ushort *)NetFragBuf;
+
+				if (udp_checksum(sumptr, udp_len, xsum)) {
+					putc('U');
+					return;
+				}
+			}
+#endif /* CONFIG_UDP_CHECKSUM */
+			(*packetHandler)(NetFragBuf + 8,
+					 udp_dst,
+					 udp_src,
+					 udp_len - 8);
+			return;
+		}
+
 		/*
 		 * watch for ICMP host redirects
 		 *
@@ -1502,26 +1636,8 @@ NetReceive(volatile uchar * inpkt, int l
 			sumlen = ntohs(ip->udp_len);
 			sumptr = (ushort *) &(ip->udp_src);
 
-			while (sumlen > 1) {
-				ushort sumdata;
-
-				sumdata = *sumptr++;
-				xsum += ntohs(sumdata);
-				sumlen -= 2;
-			}
-			if (sumlen > 0) {
-				ushort sumdata;
-
-				sumdata = *(unsigned char *) sumptr;
-				sumdata = (sumdata << 8) & 0xff00;
-				xsum += sumdata;
-			}
-			while ((xsum >> 16) != 0) {
-				xsum = (xsum & 0x0000ffff) + ((xsum >> 16) & 0x0000ffff);
-			}
-			if ((xsum != 0x00000000) && (xsum != 0x0000ffff)) {
-				printf(" UDP wrong checksum %08lx %08x\n",
-					xsum, ntohs(ip->udp_xsum));
+			if (udp_checksum(sumptr, sumlen, xsum)) {
+				putc('U');
 				return;
 			}
 		}
--- u-boot.git.orig/net/tftp.c
+++ u-boot.git/net/tftp.c
@@ -456,6 +456,7 @@ TftpTimeout (void)
 void
 TftpStart (void)
 {
+	char *s, *err;
 #ifdef CONFIG_TFTP_PORT
 	char *ep;             /* Environment pointer */
 #endif
@@ -518,6 +519,27 @@ TftpStart (void)
 
 	puts ("Loading: *\b");
 
+	/* Get alternate tftp_block_size */
+	if ((s = getenv("tftp_block_size")) != NULL) {
+		err = NULL;
+
+		TftpBlkSizeOption = simple_strtoul(s, &err, 10);
+		if (*err) {
+			printf("ERR: \"tftp_block_size\" is not a number\n");
+			TftpBlkSizeOption = TFTP_BLOCK_SIZE;
+		}
+		/*
+		 * Reject values which require extensive handling.
+		 * block size of 1428 octets (Ethernet MTU, less
+		 * the TFTP, UDP and IP header lengths).
+		 */
+		if (TftpBlkSizeOption > TFTP_BLOCK_SIZE_MAX) {
+			printf("ERR: tftp_block_sizes larger than %d not "
+			       "supported\n", TFTP_BLOCK_SIZE_MAX);
+			TftpBlkSizeOption = TFTP_BLOCK_SIZE;
+		}
+	}
+
 	NetSetTimeout (TIMEOUT * CFG_HZ, TftpTimeout);
 	NetSetHandler (TftpHandler);
 
--- u-boot.git.orig/net/tftp.h
+++ u-boot.git/net/tftp.h
@@ -8,11 +8,21 @@
 #ifndef __TFTP_H__
 #define __TFTP_H__
 
+#include <net.h>
+
 /**********************************************************************/
 /*
  *	Global functions and variables.
  */
 
+/*
+ * Maximum TFTP block size bound to max size of fragmented IP/UDP
+ * packets minus TFTP and UDP/IP overhead. TFTP overhead is 2 byte
+ * opcode and 2 byte block-number.
+ */
+#define TFTP_BLOCK_SIZE_MAX     (NET_FRAG_BUF_SIZE - sizeof(IP_t) - 4)
+
+
 /* tftp.c */
 extern void	TftpStart (void);	/* Begin TFTP get */