net: BOOTP retry timeout improvements

Currently, the BOOTP code sends out its initial request as soon as the
Ethernet driver indicates "link up". If this packet is lost or not
replied to for some reason, the code waits for a 1s timeout before
retrying. For some reason, such early packets are often lost on my
system, so this causes an annoying delay.

To optimize this, modify the BOOTP code to have very short timeouts for
the first packet transmitted, but gradually increase the timeout each
time a timeout occurs. This way, if the first packet is lost, the second
packet is transmitted quite quickly and hence the overall delay is low.
However, if there's still no response, we don't keep spewing out packets
at an insane speed.

It's arguably more correct to try and find out why the first packet is
lost. However, it seems to disappear inside my Ethenet chip; the TX chip
indicates no error during TX (not that it has much in the way of
reporting...), yet wireshark on the RX side doesn't see any packet.
FWIW, I'm using an ASIX USB Ethernet adapter. Perhaps "link up" is
reported too early or based on the wrong condition in HW, and we should
add some fixed extra delay into the driver. However, this would slow down
every link up event even if it ends up not being needed in some cases.
Having BOOTP retry quickly applies the fix/WAR to every possible
Ethernet device, and is quite simple to implement, so seems a better
solution.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>

diff --git a/net/bootp.c b/net/bootp.c
index fdb97cb56252521237baf7b2f02c94f42724cd8d..a4f6db570c6c956db2e4e18d94b6923f5458ff4e 100644 (file)
--- a/net/bootp.c
+++ b/net/bootp.c
@@ -23,12 +23,22 @@
 
 #define BOOTP_VENDOR_MAGIC     0x63825363      /* RFC1048 Magic Cookie */
 
-#define TIMEOUT                5000UL  /* Milliseconds before trying BOOTP again */
+/*
+ * The timeout for the initial BOOTP/DHCP request used to be described by a
+ * counter of fixed-length timeout periods. TIMEOUT_COUNT represents
+ * that counter
+ *
+ * Now that the timeout periods are variable (exponential backoff and retry)
+ * we convert the timeout count to the absolute time it would have take to
+ * execute that many retries, and keep sending retry packets until that time
+ * is reached.
+ */
 #ifndef CONFIG_NET_RETRY_COUNT
 # define TIMEOUT_COUNT 5               /* # of timeouts before giving up */
 #else
 # define TIMEOUT_COUNT (CONFIG_NET_RETRY_COUNT)
 #endif
+#define TIMEOUT_MS     ((3 + (TIMEOUT_COUNT * 5)) * 1000)
 
 #define PORT_BOOTPS    67              /* BOOTP server UDP port */
 #define PORT_BOOTPC    68              /* BOOTP client UDP port */
@@ -39,6 +49,8 @@
 
 ulong          BootpID;
 int            BootpTry;
+ulong          bootp_start;
+ulong          bootp_timeout;
 
 #if defined(CONFIG_CMD_DHCP)
 static dhcp_state_t dhcp_state = INIT;
@@ -327,16 +339,21 @@ BootpHandler(uchar *pkt, unsigned dest, IPaddr_t sip, unsigned src,
 static void
 BootpTimeout(void)
 {
-       if (BootpTry >= TIMEOUT_COUNT) {
+       ulong time_taken = get_timer(bootp_start);
+
+       if (time_taken >= TIMEOUT_MS) {
 #ifdef CONFIG_BOOTP_MAY_FAIL
-               puts("\nRetry count exceeded\n");
+               puts("\nRetry time exceeded\n");
                net_set_state(NETLOOP_FAIL);
 #else
-               puts("\nRetry count exceeded; starting again\n");
+               puts("\nRetry time exceeded; starting again\n");
                NetStartAgain();
 #endif
        } else {
-               NetSetTimeout(TIMEOUT, BootpTimeout);
+               bootp_timeout *= 2;
+               if (bootp_timeout > 1000)
+                       bootp_timeout = 1000;
+               NetSetTimeout(bootp_timeout, BootpTimeout);
                BootpRequest();
        }
 }
@@ -597,6 +614,13 @@ static int BootpExtended(u8 *e)
 }
 #endif
 
+void BootpReset(void)
+{
+       BootpTry = 0;
+       bootp_start = get_timer(0);
+       bootp_timeout = 10;
+}
+
 void
 BootpRequest(void)
 {
@@ -685,7 +709,7 @@ BootpRequest(void)
        iplen = BOOTP_HDR_SIZE - OPT_FIELD_SIZE + extlen;
        pktlen = eth_hdr_size + IP_UDP_HDR_SIZE + iplen;
        net_set_udp_header(iphdr, 0xFFFFFFFFL, PORT_BOOTPS, PORT_BOOTPC, iplen);
-       NetSetTimeout(SELECT_TIMEOUT, BootpTimeout);
+       NetSetTimeout(bootp_timeout, BootpTimeout);
 
 #if defined(CONFIG_CMD_DHCP)
        dhcp_state = SELECTING;
@@ -918,7 +942,7 @@ DhcpHandler(uchar *pkt, unsigned dest, IPaddr_t sip, unsigned src,
                                                htonl(BOOTP_VENDOR_MAGIC))
                                DhcpOptionsProcess((u8 *)&bp->bp_vend[4], bp);
 
-                       NetSetTimeout(TIMEOUT, BootpTimeout);
+                       NetSetTimeout(5000, BootpTimeout);
                        DhcpSendRequestPkt(bp);
 #ifdef CONFIG_SYS_BOOTFILE_PREFIX
                }

diff --git a/net/bootp.h b/net/bootp.h
index ecbcc4d5093c3dd4b2ba5e4b89e200bd32fe22d8..3b95a0a2ded87596636516c3b1b865aa79cf3aaf 100644 (file)
--- a/net/bootp.h
+++ b/net/bootp.h
@@ -65,6 +65,7 @@ extern int    BootpTry;
 
 
 /* Send a BOOTP request */
+extern void BootpReset(void);
 extern void BootpRequest(void);
 
 /****************** DHCP Support *********************/
@@ -88,8 +89,6 @@ typedef enum { INIT,
 #define DHCP_NAK      6
 #define DHCP_RELEASE  7
 
-#define SELECT_TIMEOUT 3000UL  /* Milliseconds to wait for offers */
-
 /**********************************************************************/
 
 #endif /* __BOOTP_H__ */

diff --git a/net/net.c b/net/net.c
index 0f7625fde1dc52de2df5fb3ecd91589db24c7c56..722089f3b931b58eb1fef6a766a5847ff78c3747 100644 (file)
--- a/net/net.c
+++ b/net/net.c
@@ -385,14 +385,14 @@ restart:
 #endif
 #if defined(CONFIG_CMD_DHCP)
                case DHCP:
-                       BootpTry = 0;
+                       BootpReset();
                        NetOurIP = 0;
                        DhcpRequest();          /* Basically same as BOOTP */
                        break;
 #endif
 
                case BOOTP:
-                       BootpTry = 0;
+                       BootpReset();
                        NetOurIP = 0;
                        BootpRequest();
                        break;