/** Create a TCP segment usable for passing to tcp_input */
struct pbuf*
tcp_create_segment(ip_addr_t* src_ip, ip_addr_t* dst_ip,
u16_t src_port, u16_t dst_port, void* data, size_t data_len,
u32_t seqno, u32_t ackno, u8_t headerflags)
{
struct pbuf* p;
struct ip_hdr* iphdr;
struct tcp_hdr* tcphdr;
u16_t pbuf_len = (u16_t)(sizeof(struct ip_hdr) + sizeof(struct tcp_hdr) + data_len);
p = pbuf_alloc(PBUF_RAW, pbuf_len, PBUF_POOL);
EXPECT_RETNULL(p != NULL);
EXPECT_RETNULL(p->next == NULL);
memset(p->payload, 0, p->len);
iphdr = p->payload;
/* fill IP header */
iphdr->dest.addr = dst_ip->addr;
iphdr->src.addr = src_ip->addr;
IPH_VHLTOS_SET(iphdr, 4, IP_HLEN / 4, 0);
IPH_LEN_SET(iphdr, htons(p->tot_len));
IPH_CHKSUM_SET(iphdr, inet_chksum(iphdr, IP_HLEN));
pbuf_header(p, -(s16_t)sizeof(struct ip_hdr));
tcphdr = p->payload;
tcphdr->src = htons(src_port);
tcphdr->dest = htons(dst_port);
tcphdr->seqno = htonl(seqno);
tcphdr->ackno = htonl(ackno);
TCPH_HDRLEN_SET(tcphdr, sizeof(struct tcp_hdr)/4);
TCPH_FLAGS_SET(tcphdr, headerflags);
tcphdr->wnd = htons(TCP_WND);
/* copy data */
memcpy((char*)tcphdr + sizeof(struct tcp_hdr), data, data_len);
/* calculate checksum */
tcphdr->chksum = inet_chksum_pseudo(p, src_ip, dst_ip,
IP_PROTO_TCP, p->tot_len);
pbuf_header(p, sizeof(struct ip_hdr));
return p;
}
/** Create a TCP segment usable for passing to tcp_input */
static struct pbuf*
tcp_create_segment_wnd(ip_addr_t* src_ip, ip_addr_t* dst_ip,
u16_t src_port, u16_t dst_port, void* data, size_t data_len,
u32_t seqno, u32_t ackno, u8_t headerflags, u16_t wnd)
{
struct pbuf *p, *q;
struct ip_hdr* iphdr;
struct tcp_hdr* tcphdr;
u16_t pbuf_len = (u16_t)(sizeof(struct ip_hdr) + sizeof(struct tcp_hdr) + data_len);
LWIP_ASSERT("data_len too big", data_len <= 0xFFFF);
p = pbuf_alloc(PBUF_RAW, pbuf_len, PBUF_POOL);
EXPECT_RETNULL(p != NULL);
/* first pbuf must be big enough to hold the headers */
EXPECT_RETNULL(p->len >= (sizeof(struct ip_hdr) + sizeof(struct tcp_hdr)));
if (data_len > 0) {
/* first pbuf must be big enough to hold at least 1 data byte, too */
EXPECT_RETNULL(p->len > (sizeof(struct ip_hdr) + sizeof(struct tcp_hdr)));
}
for(q = p; q != NULL; q = q->next) {
memset(q->payload, 0, q->len);
}
iphdr = (struct ip_hdr*)p->payload;
/* fill IP header */
iphdr->dest.addr = ip_2_ip4(dst_ip)->addr;
iphdr->src.addr = ip_2_ip4(src_ip)->addr;
IPH_VHL_SET(iphdr, 4, IP_HLEN / 4);
IPH_TOS_SET(iphdr, 0);
IPH_LEN_SET(iphdr, htons(p->tot_len));
IPH_CHKSUM_SET(iphdr, inet_chksum(iphdr, IP_HLEN));
/* let p point to TCP header */
pbuf_header(p, -(s16_t)sizeof(struct ip_hdr));
tcphdr = (struct tcp_hdr*)p->payload;
tcphdr->src = htons(src_port);
tcphdr->dest = htons(dst_port);
tcphdr->seqno = htonl(seqno);
tcphdr->ackno = htonl(ackno);
TCPH_HDRLEN_SET(tcphdr, sizeof(struct tcp_hdr)/4);
TCPH_FLAGS_SET(tcphdr, headerflags);
tcphdr->wnd = htons(wnd);
if (data_len > 0) {
/* let p point to TCP data */
pbuf_header(p, -(s16_t)sizeof(struct tcp_hdr));
/* copy data */
pbuf_take(p, data, (u16_t)data_len);
/* let p point to TCP header again */
pbuf_header(p, sizeof(struct tcp_hdr));
}
/* calculate checksum */
tcphdr->chksum = ip_chksum_pseudo(p,
IP_PROTO_TCP, p->tot_len, src_ip, dst_ip);
pbuf_header(p, sizeof(struct ip_hdr));
return p;
}
