Ping doesn‘t work
Ping from U-Boot to a host should work. Ping from a host to U-Boot should not.
U-Boot uses a polling interface for networking - if you have not run a command, it will not respond to any packets.
uboot-ping代码学习笔记
2011-02-20, root
最近这两天学习了uboot的ping源代码，现在做一下笔记。
uboot ：v1.1.6
uboot从start.s启动后会跳转到lib_arm/board.c里的start_armboot函数，从这以后都
是C语言代码。start_armboot做了一些初始化化然后在死循环里调用main_loop函数 ：
/* main_loop() can return to retry autoboot, if so just run it again. */
for (;;) {
main_loop ();
}
main_loop是在;common/main.c中定义的，下面是从串中读取命令然后执行的一部分代码：
for (;;) {
len = readline (CFG_PROMPT); //从串口读入命令
flag = 0; /* assume no special flags for now */
if (len > 0)
strcpy (lastcommand, console_buffer);
else if (len == 0)
flag |= CMD_FLAG_REPEAT;
}
if (len == -1)
puts ("<INTERRUPT>/n");
else
rc = run_command (lastcommand, flag); // 执行命令
if (rc <= 0) {
/* invalid command or not repeatable, forget it */
lastcommand[0] = 0;
}
}
run_command首先调用find_command在命令列表里查找到输入的命令：
/* Look up command in command table */
if ((cmdtp = find_cmd(argv[0])) == NULL) {
printf ("Unknown command ‘%s‘ - try ‘help‘/n", argv[0]);
rc = -1; /* give up after bad command */
continue;
}
find_cmd返回的是cmd_tbl_t类型，cmd_tbl_t里有命令对应的执行函数，再调用具体的
执行函数来执行命令具体的操作：
/* OK - call function to do the command */
if ((cmdtp->cmd) (cmdtp, flag, argc, argv) != 0) {
rc = -1;
}
uboot所有的命令都定义在commom目录下，ping命令在cmd_net.c文件里定义，定义如下：
U_BOOT_CMD(
ping, 2, 1, do_ping,
"ping/t- send ICMP ECHO_REQUEST to network host/n",
"pingAddress/n"
);
U_BOOT_CMD定义如下：
/*
* Monitor Command
*
* All commands use a common argument format:
*
* void function (cmd_tbl_t *cmdtp, int flag, int argc, char *argv[]);
*/
struct cmd_tbl_s {
char *name; // Command Name
int maxargs; // maximum number of arguments
int repeatable; // autorepeat allowed?
// Implementation function
int (*cmd)(struct cmd_tbl_s *, int, int, char *[]);
char *usage; // Usage message (short)
#ifdef CFG_LONGHELP
char *help; // Help message (long)
#endif
#ifdef CONFIG_AUTO_COMPLETE
// do auto completion on the arguments
int (*complete)(int argc, char *argv[], char last_char, int maxv, char *cmdv[]);
#endif
};
typedef struct cmd_tbl_s cmd_tbl_t;
#define Struct_Section __attribute__ ((unused,section (".u_boot_cmd")))
#define U_BOOT_CMD(name,maxargs,rep,cmd,usage,help) /
cmd_tbl_t __u_boot_cmd_##name Struct_Section = {#name, maxargs, rep, cmd, usage}
ping命令定义的展开：
cmd_tbl_t __u_boot_cmd_ping __attribute__ ((unused, section (".u_boot_cmd"))) = {
"ping", // name
2, // maxargs
1, // repeatable
do_ping,// (*cmd)(struct cmd_tbl_s *, int, int, char *[]);
"ping/t- send ICMP ECHO_REQUEST to network host/n", // *usage
"pingAddress/n", // *help
}
从这里可以看出，ping命令其实是调用的do_ping函数来实行具体的ping操作，do_ping的定义如下：
int do_ping (cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
{
if (argc < 2)
return -1;
NetPingIP = string_to_ip(argv[1]);
if (NetPingIP == 0) {
printf ("Usage:/n%s/n", cmdtp->usage);
return -1;
}
if (NetLoop(PING) < 0) {
printf("ping failed; host %s is not alive/n", argv[1]);
return 1;
}
printf("host %s is alive/n", argv[1]);
return 0;
}
执行ping命令:
EmbedSky> ping 192.168.1.1
dm9000 i/o: 0x20000300, id: 0x90000a46
MAC: 0a:1b:2c:3d:4e:5f
ping failed; host 192.168.1.1 is not alive
do_ping首先将192.168.1.1存在NetPingIP变量里边，然后调用NetLoop函数，如果执行成功
显示：
host 192.168.1.1 is alive
如果不成功显示：
host 192.168.1.1 is not alive
然后 退出。
NetLoop主要的工作是打包各命令对应的数据包，通过eth_send函数发送数据包，然后在死循
环里调用eth_rx来接收一个完整的ethernet帧，eth_rx收到的帧会传给NetRecive函数分析处
理。
对于ping命令，NetLoop调用PingStart
static void PingStart(void)
{
#if defined(CONFIG_NET_MULTI)
printf ("Using %s device/n", eth_get_name());
#endif /* CONFIG_NET_MULTI */
NetSetTimeout (10 * CFG_HZ, PingTimeout);
NetSetHandler (PingHandler);
PingSend();
}
PingStart首先设置接收到Ping数据包后调用的处理函数，然后调用PingSeng
发送ICMP数据包。
NetReceive处理接收到的ICMP数据包最后会调用PingHandler函数来结束Ping
操作，PingHandler只是将NetState改为NETLOOP_SUCCESS，在NetLoop里会一直
检测NetState的状态（刚进入NetLoop函数的时候NetState为NETLOOP_CONTINUE），
如果为 NETLOOP_SUCCESS 或NETLOOP_FAIL则NetLoop就会退出：
switch (NetState) {
case NETLOOP_RESTART:
#ifdef CONFIG_NET_MULTI
NetRestarted = 1;
#endif
goto restart;
case NETLOOP_SUCCESS:
if (NetBootFileXferSize > 0) {
char buf[10];
printf("Bytes transferred = %ld (%lx hex)/n",
NetBootFileXferSize,
NetBootFileXferSize);
sprintf(buf, "%lx", NetBootFileXferSize);
setenv("filesize", buf);
sprintf(buf, "%lX", (unsigned long)load_addr);
setenv("fileaddr", buf);
}
eth_halt();
return NetBootFileXferSize;
case NETLOOP_FAIL:
return (-1);
}
PingHandler (uchar * pkt, unsigned dest, unsigned src, unsigned len)
{
IPaddr_t tmp;
volatile IP_t *ip = (volatile IP_t *)pkt;
tmp = NetReadIP((void *)&ip->ip_src);
if (tmp != NetPingIP)
return;
NetState = NETLOOP_SUCCESS;
}
int PingSend(void)
{
static uchar mac[6];
volatile IP_t *ip;
volatile ushort *s;
uchar *pkt;
/* XXX always send arp request */
memcpy(mac, NetEtherNullAddr, 6);
#ifdef ET_DEBUG
printf("sending ARP for %08lx/n", NetPingIP);
#endif
NetArpWaitPacketIP = NetPingIP;
NetArpWaitPacketMAC = mac;
pkt = NetArpWaitTxPacket;
pkt += NetSetEther(pkt, mac, PROT_IP);
ip = (volatile IP_t *)pkt;
/*
* Construct an IP and ICMP header. (need to set no fragment bit - XXX)
*/
ip->ip_hl_v = 0x45; /* IP_HDR_SIZE / 4 (not including UDP) */
ip->ip_tos = 0;
ip->ip_len = htons(IP_HDR_SIZE_NO_UDP + 8);
ip->ip_id = htons(NetIPID++);
ip->ip_off = htons(0x4000); /* No fragmentation */
ip->ip_ttl = 255;
ip->ip_p = IPPROTO_ICMP; /* ICMP */
ip->ip_sum = 0;
NetCopyIP((void*)&ip->ip_src, &NetOurIP); /* already in network byte order */
NetCopyIP((void*)&ip->ip_dst, &NetPingIP); /* - "" - */
ip->ip_sum = ~NetCksum((uchar *)ip, IP_HDR_SIZE_NO_UDP / 2);
s = &ip->udp_src; /* ICMP starts here */
s[0] = htons(0x0800); /* echo-request, code */
s[1] = 0; /* checksum */
s[2] = 0; /* identifier */
s[3] = htons(PingSeqNo++); /* sequence number */
s[1] = ~NetCksum((uchar *)s, 8/2);
/* size of the waiting packet */
NetArpWaitTxPacketSize = (pkt - NetArpWaitTxPacket) + IP_HDR_SIZE_NO_UDP + 8;
/* and do the ARP request */
NetArpWaitTry = 1;
NetArpWaitTimerStart = get_timer(0);
ArpRequest();
return 1; /* waiting */
}
PingSend调用NetSetEther封装ethernet帧的头部，NetSetEther参数：
mac ：为目的host的mac，在这里全为0，因为我们只知道目的主机的ip，
现在还不知道它的mac地址
PROT_IP: 说明该ethernet帧里封装的是IP包。ethernet帧分三种类型，根据
ethernet的type来判断是哪种类型。
ethernet帧的封装：
|destination addr| source addr |type| data |crc|
6 6 2 46-1500 4 bytes
type:
PROT_IP 0x0800 /* IP protocol */
PROT_ARP 0x0806 /* IP ARP protocol */
PROT_RARP 0x8035 /* IP ARP protocol */
PingSend再将IP包封装成ICMP包：
ip->ip_p = IPPROTO_ICMP; /* ICMP */
IP包跟ethernet帧一样，也是复用的数据包，所有IP头部用1字节的proto标示来说明
IP包是哪类：
IPPROTO_ICMP 1 /* Internet Control Message Protocol */
IPPROTO_UDP 17 /* User Datagram Protocol */
IPPROTO_TCP 6 /* Transmission Control Protocol */
IPPROTO_IGMP 2 /* Internet Group Message Protocol */
ICMP将该ICMP包类型设置为echo request：
s[0] = htons(0x0800); /* echo-request, code */
封装完IP包和ICMP包后，没有立即将该ethernet帧发出去，因为现在我们只知道目的主机的
IP地址，并不知道它的ethernet地址，所以先调用ArpRequest函数取得目的主机的ethernet
地址，再ping封装的ethernet帧发送出去。
ArpRequest函数将ethernet帧封装为ARP request帧，然后广播该帧。
void ArpRequest (void)
{
int i;
volatile uchar *pkt;
ARP_t *arp;
#ifdef ET_DEBUG
printf ("ARP broadcast %d/n", NetArpWaitTry);
#endif
pkt = NetTxPacket;
pkt += NetSetEther (pkt, NetBcastAddr, PROT_ARP); // PORT_ARP说明该
// 帧为ARP帧
arp = (ARP_t *) pkt;
arp->ar_hrd = htons (ARP_ETHER);// 物理地址类型，在此为ethernet地址
arp->ar_pro = htons (PROT_IP); // 逻辑地址类型，在此为IP地址
arp->ar_hln = 6; // 物理地址类型的长度
arp->ar_pln = 4; // 逻辑地址类型的长度
arp->ar_op = htons (ARPOP_REQUEST);
memcpy (&arp->ar_data[0], NetOurEther, 6); /* source ET addr */
NetWriteIP ((uchar *) & arp->ar_data[6], NetOurIP); /* source IP addr */
for (i = 10; i < 16; ++i) {
arp->ar_data[i] = 0; /* dest ET addr = 0 */ //广播该帧
}
if ((NetArpWaitPacketIP & NetOurSubnetMask) !=
(NetOurIP & NetOurSubnetMask)) {
if (NetOurGatewayIP == 0) {
puts ("## Warning: gatewayip needed but not set/n");
NetArpWaitReplyIP = NetArpWaitPacketIP;
} else {
NetArpWaitReplyIP = NetOurGatewayIP;
}
} else {
NetArpWaitReplyIP = NetArpWaitPacketIP;
}
NetWriteIP ((uchar *) & arp->ar_data[16], NetArpWaitReplyIP); /* dest ip addr */
(void) eth_send (NetTxPacket, (pkt - NetTxPacket) + ARP_HDR_SIZE); //通过底层硬件发送该ethernet帧
}
接收ARP Replay帧和icmp echo replay帧是在NetLoop里的eth_rx进行的，eth_rx收到一个完整的帧后将该帧
传送给NetReceive处理。
NetReceive处理ARP Replay帧：
case ARPOP_REPLY: /* arp reply */
/* are we waiting for a reply */
if (!NetArpWaitPacketIP || !NetArpWaitPacketMAC)
break;
tmp = NetReadIP(&arp->ar_data[6]);
/* matched waiting packet‘s address */
if (tmp == NetArpWaitReplyIP) {
/* save address for later use */
memcpy(NetArpWaitPacketMAC, &arp->ar_data[0], 6);
/* modify header, and transmit it */
// 将返回的目标主机的mac地址放入PingSend封装的ethernet帧，然后发送该ping帧
memcpy(((Ethernet_t *)NetArpWaitTxPacket)->et_dest, NetArpWaitPacketMAC, 6);
(void) eth_send(NetArpWaitTxPacket, NetArpWaitTxPacketSize);
/* no arp request pending now */
NetArpWaitPacketIP = 0;
NetArpWaitTxPacketSize = 0;
NetArpWaitPacketMAC = NULL;
}
return;
NetReceive处理icmp echo replay帧：
case ICMP_ECHO_REPLY:
/*
* IP header OK. Pass the packet to the current handler.
*/
/* XXX point to ip packet */
(*packetHandler)((uchar *)ip, 0, 0, 0);
return;
只是调用PingHandler函数将NetState设置为NETLOOP_SUCCESS，结束NetLoop循环，
打印ping结果，然后退出do_ping函数。