/* 发送一个ICMP差错报文 */
static void
icmp_send_response(struct pbuf *p, u8_t type, u8_t code)
{
struct pbuf *q;
struct ip_hdr *iphdr;
/* we can use the echo header here */
/* 用回显请求的首部描述差错报文首部 */
struct icmp_echo_hdr *icmphdr;
/* ICMP header + IP header + 8 bytes of data */
/* 在IP层申请一个pbuf，会自动预留IP首部和以太网帧首部，
* 申请的大小是回显请求首部 + 引起差错的IP数据报首部大小 + IP数据报载荷的前8字节
*/
q = pbuf_alloc(PBUF_IP, sizeof(struct icmp_echo_hdr) + IP_HLEN + ICMP_DEST_UNREACH_DATASIZE,
PBUF_RAM);
if (q == NULL) {
/* 申请失败，则返回 */
LWIP_DEBUGF(ICMP_DEBUG, ("icmp_time_exceeded: failed to allocate pbuf for ICMP packet.\n"));
return;
}
LWIP_ASSERT("check that first pbuf can hold icmp message",
(q->len >= (sizeof(struct icmp_echo_hdr) + IP_HLEN + ICMP_DEST_UNREACH_DATASIZE)));
/* 指向引起差错的IP数据报 */
iphdr = p->payload;
LWIP_DEBUGF(ICMP_DEBUG, ("icmp_time_exceeded from "));
ip_addr_debug_print(ICMP_DEBUG, &(iphdr->src));
LWIP_DEBUGF(ICMP_DEBUG, (" to "));
ip_addr_debug_print(ICMP_DEBUG, &(iphdr->dest));
LWIP_DEBUGF(ICMP_DEBUG, ("\n"));
/* 指向ICMP报文首部 */
icmphdr = q->payload;
/* 填写类型字段 */
icmphdr->type = type;
/* 填写代码字段 */
icmphdr->code = code;
/* ICMP首部第4-7字节填0 */
icmphdr->id = 0;
icmphdr->seqno = 0;
/* copy fields from original packet */
/* 复制引起差错的IP数据报首部+8字节到ICMP数据字段 */
SMEMCPY((u8_t *)q->payload + sizeof(struct icmp_echo_hdr), (u8_t *)p->payload,
IP_HLEN + ICMP_DEST_UNREACH_DATASIZE);
/* calculate checksum */
/* 计算并填写校验和 */
icmphdr->chksum = 0;
icmphdr->chksum = inet_chksum(icmphdr, q->len);
ICMP_STATS_INC(icmp.xmit);
/* increase number of messages attempted to send */
snmp_inc_icmpoutmsgs();
/* increase number of destination unreachable messages attempted to send */
snmp_inc_icmpouttimeexcds();
/* 调用IP层函数输出ICMP报文 */
ip_output(q, NULL, &(iphdr->src), ICMP_TTL, 0, IP_PROTO_ICMP);
/* 发送完成，释放申请的ICMP用的pbuf */
pbuf_free(q);
}
void
icmp_time_exceeded(struct pbuf *p, enum icmp_te_type t)
{
struct pbuf *q;
struct ip_hdr *iphdr;
struct icmp_te_hdr *tehdr;
q = pbuf_alloc(PBUF_IP, 8 + IP_HLEN + 8, PBUF_RAM);
iphdr = p->payload;
LWIP_DEBUGF(ICMP_DEBUG, ("icmp_time_exceeded from "));
ip_addr_debug_print(ICMP_DEBUG, &(iphdr->src));
LWIP_DEBUGF(ICMP_DEBUG, (" to "));
ip_addr_debug_print(ICMP_DEBUG, &(iphdr->dest));
LWIP_DEBUGF(ICMP_DEBUG, ("\n"));
tehdr = q->payload;
ICMPH_TYPE_SET(tehdr, ICMP_TE);
ICMPH_CODE_SET(tehdr, t);
/* copy fields from original packet */
memcpy((u8_t *)q->payload + 8, (u8_t *)p->payload, IP_HLEN + 8);
/* calculate checksum */
tehdr->chksum = 0;
tehdr->chksum = inet_chksum(tehdr, q->len);
ICMP_STATS_INC(icmp.xmit);
/* increase number of messages attempted to send */
snmp_inc_icmpoutmsgs();
/* increase number of destination unreachable messages attempted to send */
snmp_inc_icmpouttimeexcds();
ip_output(q, NULL, &(iphdr->src),
ICMP_TTL, 0, IP_PROTO_ICMP);
pbuf_free(q);
}
void
icmp_dest_unreach(struct pbuf *p, enum icmp_dur_type t)
{
struct pbuf *q;
struct ip_hdr *iphdr;
struct icmp_dur_hdr *idur;
q = pbuf_alloc(PBUF_IP, 8 + IP_HLEN + 8, PBUF_RAM);
/* ICMP header + IP header + 8 bytes of data */
iphdr = p->payload;
idur = q->payload;
ICMPH_TYPE_SET(idur, ICMP_DUR);
ICMPH_CODE_SET(idur, t);
memcpy((u8_t *)q->payload + 8, p->payload, IP_HLEN + 8);
/* calculate checksum */
idur->chksum = 0;
idur->chksum = inet_chksum(idur, q->len);
ICMP_STATS_INC(icmp.xmit);
/* increase number of messages attempted to send */
snmp_inc_icmpoutmsgs();
/* increase number of destination unreachable messages attempted to send */
snmp_inc_icmpoutdestunreachs();
ip_output(q, NULL, &(iphdr->src),
ICMP_TTL, 0, IP_PROTO_ICMP);
pbuf_free(q);
}
/**
* Send an icmp packet in response to an incoming packet.
*
* @param p the input packet for which the 'unreachable' should be sent,
* p->payload pointing to the IP header
* @param type Type of the ICMP header
* @param code Code of the ICMP header
*/
static void icmp_send_response(struct pbuf *p, u8_t type, u8_t code)
{
struct pbuf *q;
struct ip_hdr *iphdr;
/* we can use the echo header here */
struct icmp_echo_hdr *icmphdr;
/* ICMP header + IP header + 8 bytes of data */
q =
pbuf_alloc(PBUF_IP,
sizeof(struct icmp_echo_hdr) + IP_HLEN +
ICMP_DEST_UNREACH_DATASIZE, PBUF_RAM);
if (q == NULL) {
LWIP_DEBUGF(ICMP_DEBUG,
("icmp_time_exceeded: failed to allocate pbuf for ICMP packet.\n"));
return;
}
LWIP_ASSERT("check that first pbuf can hold icmp message",
(q->len >=
(sizeof(struct icmp_echo_hdr) + IP_HLEN +
ICMP_DEST_UNREACH_DATASIZE)));
iphdr = p->payload;
LWIP_DEBUGF(ICMP_DEBUG, ("icmp_time_exceeded from "));
ip_addr_debug_print(ICMP_DEBUG, &(iphdr->src));
LWIP_DEBUGF(ICMP_DEBUG, (" to "));
ip_addr_debug_print(ICMP_DEBUG, &(iphdr->dest));
LWIP_DEBUGF(ICMP_DEBUG, ("\n"));
icmphdr = q->payload;
icmphdr->type = type;
icmphdr->code = code;
icmphdr->id = 0;
icmphdr->seqno = 0;
/* copy fields from original packet */
SMEMCPY((u8_t *) q->payload + sizeof(struct icmp_echo_hdr),
(u8_t *) p->payload, IP_HLEN + ICMP_DEST_UNREACH_DATASIZE);
/* calculate checksum */
icmphdr->chksum = 0;
icmphdr->chksum = inet_chksum(icmphdr, q->len);
ICMP_STATS_INC(icmp.xmit);
/* increase number of messages attempted to send */
snmp_inc_icmpoutmsgs();
/* increase number of destination unreachable messages attempted to send */
snmp_inc_icmpouttimeexcds();
ip_output(q, NULL, &(iphdr->src), ICMP_TTL, 0, IP_PROTO_ICMP);
pbuf_free(q);
}
/**
* Send an icmp packet in response to an incoming packet.
*
* @param p the input packet for which the 'unreachable' should be sent,
* p->payload pointing to the IP header
* @param type Type of the ICMP header
* @param code Code of the ICMP header
*/
static void ICACHE_FLASH_ATTR
icmp_send_response(struct pbuf *p, u8_t type, u8_t code)
{
struct pbuf *q;
struct ip_hdr *iphdr;
/* we can use the echo header here */
struct icmp_echo_hdr *icmphdr;
ip_addr_t iphdr_src;
/* ICMP header + IP header + 8 bytes of data */
//为差错报文申请pbuf空间，pbuf中预留IP首部和以太网首部空间，pbuf数据区
//长度=差错报文首部+差错报文数据长度(IP首部长度+8)
q = pbuf_alloc(PBUF_IP, sizeof(struct icmp_echo_hdr) + IP_HLEN + ICMP_DEST_UNREACH_DATASIZE,
PBUF_RAM);
if (q == NULL) {//失败，返回
LWIP_DEBUGF(ICMP_DEBUG, ("icmp_time_exceeded: failed to allocate pbuf for ICMP packet.\n"));
return;
}
LWIP_ASSERT("check that first pbuf can hold icmp message",
(q->len >= (sizeof(struct icmp_echo_hdr) + IP_HLEN + ICMP_DEST_UNREACH_DATASIZE)));
iphdr = (struct ip_hdr *)p->payload;//指向引起差错的IP数据包首部
LWIP_DEBUGF(ICMP_DEBUG, ("icmp_time_exceeded from "));
ip_addr_debug_print(ICMP_DEBUG, &(iphdr->src));
LWIP_DEBUGF(ICMP_DEBUG, (" to "));
ip_addr_debug_print(ICMP_DEBUG, &(iphdr->dest));
LWIP_DEBUGF(ICMP_DEBUG, ("\n"));
icmphdr = (struct icmp_echo_hdr *)q->payload;//指向差错报文首部
icmphdr->type = type;//填写类型字段
icmphdr->code = code;//填写代码字段
icmphdr->id = 0;//对于目的不可达和数据报超时
icmphdr->seqno = 0;//报文，首部剩余的4个字节都为0
/* copy fields from original packet 将引起差错的IP数据报的IP首部+8字节数据拷贝到差错报文数据区*/
SMEMCPY((u8_t *)q->payload + sizeof(struct icmp_echo_hdr), (u8_t *)p->payload,
IP_HLEN + ICMP_DEST_UNREACH_DATASIZE);
/* calculate checksum */
icmphdr->chksum = 0;//报文校验和字段清0
icmphdr->chksum = inet_chksum(icmphdr, q->len);//计算填写校验和
ICMP_STATS_INC(icmp.xmit);
/* increase number of messages attempted to send */
snmp_inc_icmpoutmsgs();
/* increase number of destination unreachable messages attempted to send */
snmp_inc_icmpouttimeexcds();
ip_addr_copy(iphdr_src, iphdr->src);
ip_output(q, NULL, &iphdr_src, ICMP_TTL, 0, IP_PROTO_ICMP);//调用IP层函数输出ICMP报文
pbuf_free(q);
}
/**
* Send a 'time exceeded' packet, called from ip_forward() if TTL is 0.
*
* @param p the input packet for which the 'time exceeded' should be sent,
* p->payload pointing to the IP header
* @param t type of the 'time exceeded' packet
*/
void
icmp_time_exceeded(struct pbuf *p, enum icmp_te_type t)
{
struct pbuf *q;
struct ip_hdr *iphdr;
struct icmp_te_hdr *tehdr;
/* ICMP header + IP header + 8 bytes of data */
q = pbuf_alloc(PBUF_IP, sizeof(struct icmp_dur_hdr) + IP_HLEN + ICMP_DEST_UNREACH_DATASIZE,
PBUF_RAM);
if (q == NULL) {
LWIP_DEBUGF(ICMP_DEBUG, ("icmp_time_exceeded: failed to allocate pbuf for ICMP packet.\n"));
return;
}
LWIP_ASSERT("check that first pbuf can hold icmp message",
(q->len >= (sizeof(struct icmp_dur_hdr) + IP_HLEN + ICMP_DEST_UNREACH_DATASIZE)));
iphdr = (struct ip_hdr *) p->payload;
LWIP_DEBUGF(ICMP_DEBUG, ("icmp_time_exceeded from "));
ip_addr_debug_print(ICMP_DEBUG, &(iphdr->src));
LWIP_DEBUGF(ICMP_DEBUG, (" to "));
ip_addr_debug_print(ICMP_DEBUG, &(iphdr->dest));
LWIP_DEBUGF(ICMP_DEBUG, ("\n"));
tehdr = (struct icmp_te_hdr *) q->payload;
ICMPH_TYPE_SET(tehdr, ICMP_TE);
ICMPH_CODE_SET(tehdr, t);
/* copy fields from original packet */
SMEMCPY((u8_t *)q->payload + sizeof(struct icmp_dur_hdr), (u8_t *)p->payload,
IP_HLEN + ICMP_DEST_UNREACH_DATASIZE);
/* calculate checksum */
tehdr->chksum = 0;
tehdr->chksum = inet_chksum(tehdr, q->len);
ICMP_STATS_INC(icmp.xmit);
/* increase number of messages attempted to send */
snmp_inc_icmpoutmsgs();
/* increase number of destination unreachable messages attempted to send */
snmp_inc_icmpouttimeexcds();
ip_output(q, NULL, &(iphdr->src), ICMP_TTL, 0, IP_PROTO_ICMP);
pbuf_free(q);
}
/**
* Send an icmp 'destination unreachable' packet, called from ip_input() if
* the transport layer protocol is unknown and from udp_input() if the local
* port is not bound.
*
* @param p the input packet for which the 'unreachable' should be sent,
* p->payload pointing to the IP header
* @param t type of the 'unreachable' packet
*/
void
icmp_dest_unreach(struct pbuf *p, enum icmp_dur_type t)
{
struct pbuf *q;
struct ip_hdr *iphdr;
struct icmp_dur_hdr *idur;
/* ICMP header + IP header + 8 bytes of data */
q = pbuf_alloc(PBUF_IP, sizeof(struct icmp_dur_hdr) + IP_HLEN + ICMP_DEST_UNREACH_DATASIZE,
PBUF_RAM);
if (q == NULL) {
LWIP_DEBUGF(ICMP_DEBUG, ("icmp_dest_unreach: failed to allocate pbuf for ICMP packet.\n"));
return;
}
LWIP_ASSERT("check that first pbuf can hold icmp message",
(q->len >= (sizeof(struct icmp_dur_hdr) + IP_HLEN + ICMP_DEST_UNREACH_DATASIZE)));
iphdr = p->payload;
idur = q->payload;
ICMPH_TYPE_SET(idur, ICMP_DUR);
ICMPH_CODE_SET(idur, t);
SMEMCPY((u8_t *)q->payload + sizeof(struct icmp_dur_hdr), p->payload,
IP_HLEN + ICMP_DEST_UNREACH_DATASIZE);
/* calculate checksum */
idur->chksum = 0;
idur->chksum = inet_chksum(idur, q->len);
ICMP_STATS_INC(icmp.xmit);
/* increase number of messages attempted to send */
snmp_inc_icmpoutmsgs();
/* increase number of destination unreachable messages attempted to send */
snmp_inc_icmpoutdestunreachs();
ip_output(q, NULL, &(iphdr->src), ICMP_TTL, 0, IP_PROTO_ICMP);
pbuf_free(q);
}
/**
* Processes ICMP input packets, called from ip_input().
*
* Currently only processes icmp echo requests and sends
* out the echo response.
*
* @param p the icmp echo request packet, p->payload pointing to the icmp header
* @param inp the netif on which this packet was received
*/
void
icmp_input(struct pbuf *p, struct netif *inp)
{
u8_t type;
#ifdef LWIP_DEBUG
u8_t code;
#endif /* LWIP_DEBUG */
struct icmp_echo_hdr *iecho;
struct ip_hdr *iphdr;
s16_t hlen;
ICMP_STATS_INC(icmp.recv);
snmp_inc_icmpinmsgs();
iphdr = (struct ip_hdr *)ip_current_header();
hlen = IPH_HL(iphdr) * 4;
if (p->len < sizeof(u16_t)*2) {
LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: short ICMP (%"U16_F" bytes) received\n", p->tot_len));
goto lenerr;
}
type = *((u8_t *)p->payload);
#ifdef LWIP_DEBUG
code = *(((u8_t *)p->payload)+1);
#endif /* LWIP_DEBUG */
switch (type) {
case ICMP_ER:
/* This is OK, echo reply might have been parsed by a raw PCB
(as obviously, an echo request has been sent, too). */
break;
case ICMP_ECHO:
#if !LWIP_MULTICAST_PING || !LWIP_BROADCAST_PING
{
int accepted = 1;
#if !LWIP_MULTICAST_PING
/* multicast destination address? */
if (ip_addr_ismulticast(ip_current_dest_addr())) {
accepted = 0;
}
#endif /* LWIP_MULTICAST_PING */
#if !LWIP_BROADCAST_PING
/* broadcast destination address? */
if (ip_addr_isbroadcast(ip_current_dest_addr(), inp)) {
accepted = 0;
}
#endif /* LWIP_BROADCAST_PING */
/* broadcast or multicast destination address not acceptd? */
if (!accepted) {
LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: Not echoing to multicast or broadcast pings\n"));
ICMP_STATS_INC(icmp.err);
pbuf_free(p);
return;
}
}
#endif /* !LWIP_MULTICAST_PING || !LWIP_BROADCAST_PING */
LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: ping\n"));
if (p->tot_len < sizeof(struct icmp_echo_hdr)) {
LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: bad ICMP echo received\n"));
goto lenerr;
}
#if CHECKSUM_CHECK_ICMP
if (inet_chksum_pbuf(p) != 0) {
LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: checksum failed for received ICMP echo\n"));
pbuf_free(p);
ICMP_STATS_INC(icmp.chkerr);
snmp_inc_icmpinerrors();
return;
}
#endif
#if LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN
if (pbuf_header(p, (PBUF_IP_HLEN + PBUF_LINK_HLEN))) {
/* p is not big enough to contain link headers
* allocate a new one and copy p into it
*/
struct pbuf *r;
/* switch p->payload to ip header */
if (pbuf_header(p, hlen)) {
LWIP_ASSERT("icmp_input: moving p->payload to ip header failed\n", 0);
goto memerr;
}
/* allocate new packet buffer with space for link headers */
r = pbuf_alloc(PBUF_LINK, p->tot_len, PBUF_RAM);
if (r == NULL) {
LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: allocating new pbuf failed\n"));
goto memerr;
}
LWIP_ASSERT("check that first pbuf can hold struct the ICMP header",
(r->len >= hlen + sizeof(struct icmp_echo_hdr)));
/* copy the whole packet including ip header */
if (pbuf_copy(r, p) != ERR_OK) {
LWIP_ASSERT("icmp_input: copying to new pbuf failed\n", 0);
goto memerr;
}
iphdr = (struct ip_hdr *)r->payload;
/* switch r->payload back to icmp header */
if (pbuf_header(r, -hlen)) {
LWIP_ASSERT("icmp_input: restoring original p->payload failed\n", 0);
goto memerr;
}
/* free the original p */
pbuf_free(p);
/* we now have an identical copy of p that has room for link headers */
p = r;
} else {
/* restore p->payload to point to icmp header */
if (pbuf_header(p, -(s16_t)(PBUF_IP_HLEN + PBUF_LINK_HLEN))) {
LWIP_ASSERT("icmp_input: restoring original p->payload failed\n", 0);
goto memerr;
}
}
#endif /* LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN */
/* At this point, all checks are OK. */
/* We generate an answer by switching the dest and src ip addresses,
* setting the icmp type to ECHO_RESPONSE and updating the checksum. */
iecho = (struct icmp_echo_hdr *)p->payload;
ip_addr_copy(iphdr->src, *ip_current_dest_addr());
ip_addr_copy(iphdr->dest, *ip_current_src_addr());
ICMPH_TYPE_SET(iecho, ICMP_ER);
#if CHECKSUM_GEN_ICMP
/* adjust the checksum */
if (iecho->chksum > PP_HTONS(0xffffU - (ICMP_ECHO << 8))) {
iecho->chksum += PP_HTONS(ICMP_ECHO << 8) + 1;
} else {
iecho->chksum += PP_HTONS(ICMP_ECHO << 8);
}
#else /* CHECKSUM_GEN_ICMP */
iecho->chksum = 0;
#endif /* CHECKSUM_GEN_ICMP */
/* Set the correct TTL and recalculate the header checksum. */
IPH_TTL_SET(iphdr, ICMP_TTL);
IPH_CHKSUM_SET(iphdr, 0);
#if CHECKSUM_GEN_IP
IPH_CHKSUM_SET(iphdr, inet_chksum(iphdr, IP_HLEN));
#endif /* CHECKSUM_GEN_IP */
ICMP_STATS_INC(icmp.xmit);
/* increase number of messages attempted to send */
snmp_inc_icmpoutmsgs();
/* increase number of echo replies attempted to send */
snmp_inc_icmpoutechoreps();
if(pbuf_header(p, hlen)) {
LWIP_ASSERT("Can't move over header in packet", 0);
} else {
err_t ret;
/* send an ICMP packet, src addr is the dest addr of the curren packet */
ret = ip_output_if(p, ip_current_dest_addr(), IP_HDRINCL,
ICMP_TTL, 0, IP_PROTO_ICMP, inp);
if (ret != ERR_OK) {
LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: ip_output_if returned an error: %c.\n", ret));
}
}
break;
default:
LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: ICMP type %"S16_F" code %"S16_F" not supported.\n",
(s16_t)type, (s16_t)code));
ICMP_STATS_INC(icmp.proterr);
ICMP_STATS_INC(icmp.drop);
}
pbuf_free(p);
return;
lenerr:
pbuf_free(p);
ICMP_STATS_INC(icmp.lenerr);
snmp_inc_icmpinerrors();
return;
#if LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN
memerr:
pbuf_free(p);
ICMP_STATS_INC(icmp.err);
snmp_inc_icmpinerrors();
return;
#endif /* LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN */
}
/**
* Processes ICMP input packets, called from ip_input().
*
* Currently only processes icmp echo requests and sends
* out the echo response.
*
* @param p the icmp echo request packet, p->payload pointing to the ip header
* @param inp the netif on which this packet was received
*/
void
icmp_input(struct pbuf *p, struct netif *inp)
{
u8_t type;
#ifdef LWIP_DEBUG
u8_t code;
#endif /* LWIP_DEBUG */
struct icmp_echo_hdr *iecho;
struct ip_hdr *iphdr;
struct ip_addr tmpaddr;
s16_t hlen;
u8_t iptxt[20];
volatile u8_t iptab[4];
u32_t IPaddress;
ICMP_STATS_INC(icmp.recv);
snmp_inc_icmpinmsgs();
iphdr = p->payload;
hlen = IPH_HL(iphdr) * 4;
if (pbuf_header(p, -hlen) || (p->tot_len < sizeof(u16_t)*2)) {
LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: short ICMP (%"U16_F" bytes) received\n", p->tot_len));
goto lenerr;
}
IPaddress = iphdr->src.addr;
/* read its IP address */
iptab[0] = (u8_t)(IPaddress >> 24);
iptab[1] = (u8_t)(IPaddress >> 16);
iptab[2] = (u8_t)(IPaddress >> 8);
iptab[3] = (u8_t)(IPaddress);
sprintf((char*)iptxt, "Ping: %d.%d.%d.%d ", iptab[3], iptab[2], iptab[1], iptab[0]);
LCD_DisplayStringLine(Line4, iptxt);
printf("\n\r%s", iptxt);
type = *((u8_t *)p->payload);
#ifdef LWIP_DEBUG
code = *(((u8_t *)p->payload)+1);
#endif /* LWIP_DEBUG */
switch (type) {
case ICMP_ECHO:
#if !LWIP_MULTICAST_PING || !LWIP_BROADCAST_PING
{
int accepted = 1;
#if !LWIP_MULTICAST_PING
/* multicast destination address? */
if (ip_addr_ismulticast(&iphdr->dest)) {
accepted = 0;
}
#endif /* LWIP_MULTICAST_PING */
#if !LWIP_BROADCAST_PING
/* broadcast destination address? */
if (ip_addr_isbroadcast(&iphdr->dest, inp)) {
accepted = 0;
}
#endif /* LWIP_BROADCAST_PING */
/* broadcast or multicast destination address not acceptd? */
if (!accepted) {
LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: Not echoing to multicast or broadcast pings\n"));
ICMP_STATS_INC(icmp.err);
pbuf_free(p);
return;
}
}
#endif /* !LWIP_MULTICAST_PING || !LWIP_BROADCAST_PING */
LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: ping\n"));
if (p->tot_len < sizeof(struct icmp_echo_hdr)) {
LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: bad ICMP echo received\n"));
goto lenerr;
}
if (inet_chksum_pbuf(p) != 0) {
LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: checksum failed for received ICMP echo\n"));
pbuf_free(p);
ICMP_STATS_INC(icmp.chkerr);
snmp_inc_icmpinerrors();
return;
}
#if LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN
if (pbuf_header(p, (PBUF_IP_HLEN + PBUF_LINK_HLEN))) {
/* p is not big enough to contain link headers
* allocate a new one and copy p into it
*/
struct pbuf *r;
/* switch p->payload to ip header */
if (pbuf_header(p, hlen)) {
LWIP_ASSERT("icmp_input: moving p->payload to ip header failed\n", 0);
goto memerr;
}
/* allocate new packet buffer with space for link headers */
r = pbuf_alloc(PBUF_LINK, p->tot_len, PBUF_RAM);
if (r == NULL) {
LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: allocating new pbuf failed\n"));
goto memerr;
}
LWIP_ASSERT("check that first pbuf can hold struct the ICMP header",
(r->len >= hlen + sizeof(struct icmp_echo_hdr)));
/* copy the whole packet including ip header */
if (pbuf_copy(r, p) != ERR_OK) {
LWIP_ASSERT("icmp_input: copying to new pbuf failed\n", 0);
goto memerr;
}
iphdr = r->payload;
/* switch r->payload back to icmp header */
if (pbuf_header(r, -hlen)) {
LWIP_ASSERT("icmp_input: restoring original p->payload failed\n", 0);
goto memerr;
}
/* free the original p */
pbuf_free(p);
/* we now have an identical copy of p that has room for link headers */
p = r;
} else {
/* restore p->payload to point to icmp header */
if (pbuf_header(p, -(s16_t)(PBUF_IP_HLEN + PBUF_LINK_HLEN))) {
LWIP_ASSERT("icmp_input: restoring original p->payload failed\n", 0);
goto memerr;
}
}
#endif /* LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN */
/* At this point, all checks are OK. */
/* We generate an answer by switching the dest and src ip addresses,
* setting the icmp type to ECHO_RESPONSE and updating the checksum. */
iecho = p->payload;
tmpaddr.addr = iphdr->src.addr;
iphdr->src.addr = iphdr->dest.addr;
iphdr->dest.addr = tmpaddr.addr;
ICMPH_TYPE_SET(iecho, ICMP_ER);
/* This part of code has been modified by ST's MCD Application Team */
/* To use the Checksum Offload Engine for the putgoing ICMP packets,
the ICMP checksum field should be set to 0, this is required only for Tx ICMP*/
#ifdef CHECKSUM_BY_HARDWARE
iecho->chksum = 0;
#else
/* adjust the checksum */
if (iecho->chksum >= htons(0xffff - (ICMP_ECHO << 8))) {
iecho->chksum += htons(ICMP_ECHO << 8) + 1;
} else {
iecho->chksum += htons(ICMP_ECHO << 8);
}
#endif
/* Set the correct TTL and recalculate the header checksum. */
IPH_TTL_SET(iphdr, ICMP_TTL);
IPH_CHKSUM_SET(iphdr, 0);
#if CHECKSUM_GEN_IP
IPH_CHKSUM_SET(iphdr, inet_chksum(iphdr, IP_HLEN));
#endif /* CHECKSUM_GEN_IP */
ICMP_STATS_INC(icmp.xmit);
/* increase number of messages attempted to send */
snmp_inc_icmpoutmsgs();
/* increase number of echo replies attempted to send */
snmp_inc_icmpoutechoreps();
if(pbuf_header(p, hlen)) {
LWIP_ASSERT("Can't move over header in packet", 0);
} else {
err_t ret;
ret = ip_output_if(p, &(iphdr->src), IP_HDRINCL,
ICMP_TTL, 0, IP_PROTO_ICMP, inp);
if (ret != ERR_OK) {
LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: ip_output_if returned an error: %c.\n", ret));
}
}
break;
default:
LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: ICMP type %"S16_F" code %"S16_F" not supported.\n",
(s16_t)type, (s16_t)code));
ICMP_STATS_INC(icmp.proterr);
ICMP_STATS_INC(icmp.drop);
}
pbuf_free(p);
return;
lenerr:
pbuf_free(p);
ICMP_STATS_INC(icmp.lenerr);
snmp_inc_icmpinerrors();
return;
#if LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN
memerr:
pbuf_free(p);
ICMP_STATS_INC(icmp.err);
snmp_inc_icmpinerrors();
return;
#endif /* LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN */
}
/* 调用途径：ethernetif_input() -> ethernet_input() -> ip_input() -> icmp_input()*/
void
icmp_input(struct pbuf *p, struct netif *inp)
{
u8_t type;
#ifdef LWIP_DEBUG
u8_t code;
#endif /* LWIP_DEBUG */
struct icmp_echo_hdr *iecho;
struct ip_hdr *iphdr;
/* IP 地址 */
struct ip_addr tmpaddr;
s16_t hlen;
ICMP_STATS_INC(icmp.recv);
snmp_inc_icmpinmsgs();
/* 指向IP首部 */
iphdr = p->payload;
/* 获得IP报头长度 */
hlen = IPH_HL(iphdr) * 4;
/* pbuf的payload向后移动到IP载荷，即ICMP报头处
* 如果IP的载荷小于4字节，则跳到lenerr处，释放pbuf
*/
if (pbuf_header(p, -hlen) || (p->tot_len < sizeof(u16_t)*2)) {
LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: short ICMP (%"U16_F" bytes) received\n", p->tot_len));
goto lenerr;
}
/* 获取ICMP报头中的类型 */
type = *((u8_t *)p->payload);
#ifdef LWIP_DEBUG
code = *(((u8_t *)p->payload)+1);
#endif /* LWIP_DEBUG */
switch (type) {
/* 如果ICMP类型是回显请求 */
case ICMP_ECHO:
/* 先检查目的IP地址是否合法 */
#if !LWIP_MULTICAST_PING || !LWIP_BROADCAST_PING
{
/* accepted表示是否对ICMP回显请求进行回应 */
int accepted = 1;
#if !LWIP_MULTICAST_PING
/* multicast destination address? */
/* 如果目的IP地址是多播地址，则不回应 */
if (ip_addr_ismulticast(&iphdr->dest)) {
accepted = 0;
}
#endif /* LWIP_MULTICAST_PING */
#if !LWIP_BROADCAST_PING
/* broadcast destination address? */
/* 如果目的IP地址是广播地址，则不回应 */
if (ip_addr_isbroadcast(&iphdr->dest, inp)) {
accepted = 0;
}
#endif /* LWIP_BROADCAST_PING */
/* broadcast or multicast destination address not acceptd? */
/* 如果不回应，则释放pbuf后，返回 */
if (!accepted) {
LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: Not echoing to multicast or broadcast pings\n"));
ICMP_STATS_INC(icmp.err);
pbuf_free(p);
return;
}
}
#endif /* !LWIP_MULTICAST_PING || !LWIP_BROADCAST_PING */
LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: ping\n"));
/* 检查ICMP报文长度是否合法,ICMP报文总长度不能小于ICMP报头长度8字节 */
if (p->tot_len < sizeof(struct icmp_echo_hdr)) {
LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: bad ICMP echo received\n"));
/* 跳到lenerr处执行返回操作 */
goto lenerr;
}
/* 计算ICMP的校验和是否正确 */
if (inet_chksum_pbuf(p) != 0) {
LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: checksum failed for received ICMP echo\n"));
/* ICMP校验和错误，则释放pbuf，并返回 */
pbuf_free(p);
ICMP_STATS_INC(icmp.chkerr);
snmp_inc_icmpinerrors();
return;
}
#if LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN
if (pbuf_header(p, (PBUF_IP_HLEN + PBUF_LINK_HLEN))) {
/* p is not big enough to contain link headers
* allocate a new one and copy p into it
*/
struct pbuf *r;
/* switch p->payload to ip header */
if (pbuf_header(p, hlen)) {
LWIP_ASSERT("icmp_input: moving p->payload to ip header failed\n", 0);
goto memerr;
}
/* allocate new packet buffer with space for link headers */
r = pbuf_alloc(PBUF_LINK, p->tot_len, PBUF_RAM);
if (r == NULL) {
LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: allocating new pbuf failed\n"));
goto memerr;
}
LWIP_ASSERT("check that first pbuf can hold struct the ICMP header",
(r->len >= hlen + sizeof(struct icmp_echo_hdr)));
/* copy the whole packet including ip header */
if (pbuf_copy(r, p) != ERR_OK) {
LWIP_ASSERT("icmp_input: copying to new pbuf failed\n", 0);
goto memerr;
}
iphdr = r->payload;
/* switch r->payload back to icmp header */
if (pbuf_header(r, -hlen)) {
LWIP_ASSERT("icmp_input: restoring original p->payload failed\n", 0);
goto memerr;
}
/* free the original p */
pbuf_free(p);
/* we now have an identical copy of p that has room for link headers */
p = r;
} else {
/* restore p->payload to point to icmp header */
if (pbuf_header(p, -(s16_t)(PBUF_IP_HLEN + PBUF_LINK_HLEN))) {
LWIP_ASSERT("icmp_input: restoring original p->payload failed\n", 0);
goto memerr;
}
}
#endif /* LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN */
/* At this point, all checks are OK. */
/* We generate an answer by switching the dest and src ip addresses,
* setting the icmp type to ECHO_RESPONSE and updating the checksum. */
/* 校验完成，调整ICMP回显请求的相关字段，生成回显应答
* 交换IP数据报的源IP和目的IP地址，填写ICMP报文的类型字段，并重新计算ICMP的校验和
*/
/* 获取ICMP报头指针 */
iecho = p->payload;
/* 交换IP报头的源IP地址和目的IP地址 */
tmpaddr.addr = iphdr->src.addr;
iphdr->src.addr = iphdr->dest.addr;
iphdr->dest.addr = tmpaddr.addr;
/* 设置ICMP报文类型为回显应答 */
ICMPH_TYPE_SET(iecho, ICMP_ER);
/* adjust the checksum */
/* 调整ICMP的校验和 */
if (iecho->chksum >= htons(0xffff - (ICMP_ECHO << 8))) {
iecho->chksum += htons(ICMP_ECHO << 8) + 1;
} else {
iecho->chksum += htons(ICMP_ECHO << 8);
}
/* Set the correct TTL and recalculate the header checksum. */
/* 设置IP首部的TTL */
IPH_TTL_SET(iphdr, ICMP_TTL);
/* 计算IP首部校验和 */
IPH_CHKSUM_SET(iphdr, 0);
#if CHECKSUM_GEN_IP
IPH_CHKSUM_SET(iphdr, inet_chksum(iphdr, IP_HLEN));
#endif /* CHECKSUM_GEN_IP */
/* 注意：这里没有修改IP首部的标识字段，所以ICMP回显应答的IP首部的标识字段和
* ICMP回显请求的标识字段是相同的。理论上来说ICMP回显应答的IP首部标识字段应该
* 被修改，但为什么不修改？
* 对Linux主机进行ping，Linux主机回复的ICMP回显应答的IP首部的标识字段就修改了
*/
ICMP_STATS_INC(icmp.xmit);
/* increase number of messages attempted to send */
snmp_inc_icmpoutmsgs();
/* increase number of echo replies attempted to send */
snmp_inc_icmpoutechoreps();
/* pbuf的payload由ICMP的报头移动到IP的报头，hlen保存了IP报头的长度 */
if(pbuf_header(p, hlen)) {
LWIP_ASSERT("Can't move over header in packet", 0);
/* 移动失败 */
} else {
/* 移动成功 */
err_t ret;
/* 调用ip_output_if发送IP数据报，IP_HDRINCL表示IP首部已经填写好，并且
* pbuf的payload指向IP数据报首部，而不是IP载荷首部
*/
ret = ip_output_if(p, &(iphdr->src), IP_HDRINCL,
ICMP_TTL, 0, IP_PROTO_ICMP, inp);
if (ret != ERR_OK) {
LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: ip_output_if returned an error: %c.\n", ret));
}
}
break;
/* 如果ICMP类型不是ICMP回显请求，则直接忽略 */
default:
LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: ICMP type %"S16_F" code %"S16_F" not supported.\n",
(s16_t)type, (s16_t)code));
/* 更新统计量 */
ICMP_STATS_INC(icmp.proterr);
ICMP_STATS_INC(icmp.drop);
}
/* 释放pbuf */
pbuf_free(p);
return;
lenerr:
pbuf_free(p);
ICMP_STATS_INC(icmp.lenerr);
snmp_inc_icmpinerrors();
return;
#if LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN
memerr:
pbuf_free(p);
ICMP_STATS_INC(icmp.err);
snmp_inc_icmpinerrors();
return;
#endif /* LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN */
}
void
icmp_input(struct pbuf *p, struct netif *inp)
{
u8_t type;
u8_t code;
struct icmp_echo_hdr *iecho;
struct ip_hdr *iphdr;
struct ip_addr tmpaddr;
u16_t hlen;
u8_t *payload = NULL;
ICMP_STATS_INC(icmp.recv);
snmp_inc_icmpinmsgs();
iphdr = p->payload;
hlen = IPH_HL(iphdr) * 4;
if (p->tot_len < sizeof(u16_t)*2) {
LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: short ICMP (%"U16_F" bytes) received\n", p->tot_len));
pbuf_free(p);
ICMP_STATS_INC(icmp.lenerr);
snmp_inc_icmpinerrors();
return;
}
payload = (u8_t *)p->payload + hlen;
type = *payload;
code = *(payload+1);
switch (type) {
case ICMP_ECHO:
/* broadcast or multicast destination address? */
if (ip_addr_isbroadcast(&iphdr->dest, inp) || ip_addr_ismulticast(&iphdr->dest)) {
LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: Not echoing to multicast or broadcast pings\n"));
ICMP_STATS_INC(icmp.err);
pbuf_free(p);
return;
}
LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: ping\n"));
if (p->tot_len < sizeof(struct icmp_echo_hdr)) {
LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: bad ICMP echo received\n"));
pbuf_free(p);
ICMP_STATS_INC(icmp.lenerr);
snmp_inc_icmpinerrors();
return;
}
iecho = (struct icmp_echo_hdr *)payload;
if (inet_chksum_pbuf(p) != 0) {
LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: checksum failed for received ICMP echo\n"));
pbuf_free(p);
ICMP_STATS_INC(icmp.chkerr);
snmp_inc_icmpinerrors();
return;
}
tmpaddr.addr = iphdr->src.addr;
iphdr->src.addr = iphdr->dest.addr;
iphdr->dest.addr = tmpaddr.addr;
ICMPH_TYPE_SET(iecho, ICMP_ER);
/* adjust the checksum */
if (iecho->chksum >= htons(0xffff - (ICMP_ECHO << 8))) {
iecho->chksum += htons(ICMP_ECHO << 8) + 1;
} else {
iecho->chksum += htons(ICMP_ECHO << 8);
}
ICMP_STATS_INC(icmp.xmit);
/* increase number of messages attempted to send */
snmp_inc_icmpoutmsgs();
/* increase number of echo replies attempted to send */
snmp_inc_icmpoutechoreps();
pbuf_header(p, hlen);
ip_output_if(p, &(iphdr->src), IP_HDRINCL,
IPH_TTL(iphdr), 0, IP_PROTO_ICMP, inp);
break;
default:
LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: ICMP type %"S16_F" code %"S16_F" not supported.\n", (s16_t)type, (s16_t)code));
ICMP_STATS_INC(icmp.proterr);
ICMP_STATS_INC(icmp.drop);
}
pbuf_free(p);
}