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https://github.com/lwip-tcpip/lwip.git
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fixed bug #37969 SYN packet dropped as short packet in tcp_input function
This commit is contained in:
Simon Goldschmidt
parent
7fe7e1e984
commit
974f6982a1
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@ -165,6 +165,10 @@ HISTORY
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++ Bugfixes:
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2014-06-03: Simon Goldschmidt
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* tcp_impl.h, tcp_in.c: fixed bug #37969 SYN packet dropped as short packet in
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tcp_input function
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2014-05-20: Simon Goldschmidt
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* tcp_out.c: fixed bug #37184 tcp_write problem for pcbs in the SYN_SENT state
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@ -67,6 +67,9 @@
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function. */
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static struct tcp_seg inseg;
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static struct tcp_hdr *tcphdr;
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static u16_t tcphdr_opt1len;
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static u8_t* tcphdr_opt2;
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static u16_t tcp_optidx;
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static u32_t seqno, ackno;
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static u8_t flags;
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static u16_t tcplen;
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@ -150,11 +153,39 @@ tcp_input(struct pbuf *p, struct netif *inp)
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/* Move the payload pointer in the pbuf so that it points to the
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TCP data instead of the TCP header. */
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hdrlen = TCPH_HDRLEN(tcphdr);
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if(pbuf_header(p, -(hdrlen * 4))){
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/* drop short packets */
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LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_input: short packet\n"));
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TCP_STATS_INC(tcp.lenerr);
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goto dropped;
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tcphdr_opt1len = (hdrlen * 4) - TCP_HLEN;
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tcphdr_opt2 = NULL;
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if (p->len < hdrlen * 4) {
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if (p->len >= TCP_HLEN) {
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/* TCP header fits into first pbuf, options don't - data is in the next pbuf */
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u16_t optlen = tcphdr_opt1len;
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pbuf_header(p, -TCP_HLEN); /* cannot fail */
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LWIP_ASSERT("tcphdr_opt1len >= p->len", tcphdr_opt1len >= p->len);
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LWIP_ASSERT("p->next != NULL", p->next != NULL);
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tcphdr_opt1len = p->len;
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if (optlen > tcphdr_opt1len) {
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s16_t opt2len;
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/* options continue in the next pbuf: set p to zero length and hide the
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options in the next pbuf (adjusting p->tot_len) */
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u8_t phret = pbuf_header(p, -(s16_t)tcphdr_opt1len);
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LWIP_ASSERT("phret == 0", phret == 0);
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tcphdr_opt2 = (u8_t*)p->next->payload;
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opt2len = optlen - tcphdr_opt1len;
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phret = pbuf_header(p->next, -opt2len);
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LWIP_ASSERT("phret == 0", phret == 0);
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/* p->next->payload now points to the TCP data */
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/* manually adjust p->tot_len to changed p->next->tot_len change */
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p->tot_len -= opt2len;
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}
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LWIP_ASSERT("p->len == 0", p->len == 0);
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} else {
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/* drop short packets */
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LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_input: short packet\n"));
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TCP_STATS_INC(tcp.lenerr);
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goto dropped;
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}
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} else {
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pbuf_header(p, -(hdrlen * 4)); /* cannot fail */
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}
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/* Convert fields in TCP header to host byte order. */
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@ -1611,8 +1642,19 @@ tcp_receive(struct tcp_pcb *pcb)
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}
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}
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static u8_t tcp_getoptbyte(void)
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{
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if ((tcphdr_opt2 == NULL) || (tcp_optidx < tcphdr_opt1len)) {
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u8_t* opts = (u8_t *)tcphdr + TCP_HLEN;
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return opts[tcp_optidx++];
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} else {
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u8_t idx = tcp_optidx++ - tcphdr_opt1len;
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return tcphdr_opt2[idx];
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}
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}
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/**
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* Parses the options contained in the incoming segment.
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* Parses the options contained in the incoming segment.
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*
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* Called from tcp_listen_input() and tcp_process().
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* Currently, only the MSS option is supported!
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@ -1622,78 +1664,74 @@ tcp_receive(struct tcp_pcb *pcb)
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static void
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tcp_parseopt(struct tcp_pcb *pcb)
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{
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u16_t c, max_c;
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u8_t data;
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u16_t mss;
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u8_t *opts, opt;
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#if LWIP_TCP_TIMESTAMPS
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u32_t tsval;
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#endif
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opts = (u8_t *)tcphdr + TCP_HLEN;
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/* Parse the TCP MSS option, if present. */
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if (TCPH_HDRLEN(tcphdr) > 0x5) {
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max_c = (TCPH_HDRLEN(tcphdr) - 5) << 2;
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for (c = 0; c < max_c; ) {
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opt = opts[c];
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u16_t max_c = (TCPH_HDRLEN(tcphdr) - 5) << 2;
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for (tcp_optidx = 0; tcp_optidx < max_c; ) {
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u8_t opt = tcp_getoptbyte();
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switch (opt) {
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case 0x00:
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case LWIP_TCP_OPT_EOL:
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/* End of options. */
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LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_parseopt: EOL\n"));
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return;
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case 0x01:
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case LWIP_TCP_OPT_NOP:
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/* NOP option. */
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++c;
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LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_parseopt: NOP\n"));
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break;
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case 0x02:
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case LWIP_TCP_OPT_MSS:
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LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_parseopt: MSS\n"));
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if (opts[c + 1] != 0x04 || c + 0x04 > max_c) {
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if (tcp_getoptbyte() != LWIP_TCP_OPT_LEN_MSS || (tcp_optidx - 2 + LWIP_TCP_OPT_LEN_MSS) > max_c) {
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/* Bad length */
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LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_parseopt: bad length\n"));
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return;
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}
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/* An MSS option with the right option length. */
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mss = (opts[c + 2] << 8) | opts[c + 3];
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mss = (tcp_getoptbyte() << 8);
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mss |= tcp_getoptbyte();
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/* Limit the mss to the configured TCP_MSS and prevent division by zero */
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pcb->mss = ((mss > TCP_MSS) || (mss == 0)) ? TCP_MSS : mss;
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/* Advance to next option */
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c += 0x04;
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break;
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#if LWIP_WND_SCALE
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case 0x03:
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case LWIP_TCP_OPT_WS:
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LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_parseopt: WND_SCALE\n"));
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if (opts[c + 1] != 0x03 || c + 0x03 > max_c) {
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if (tcp_getoptbyte() != LWIP_TCP_OPT_LEN_WS || (tcp_optidx - 2 + LWIP_TCP_OPT_LEN_WS) > max_c) {
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/* Bad length */
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LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_parseopt: bad length\n"));
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return;
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}
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/* If syn was received with wnd scale option,
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activate wnd scale opt */
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data = tcp_getoptbyte();
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if (flags & TCP_SYN) {
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/* An WND_SCALE option with the right option length. */
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pcb->snd_scale = opts[c + 2];
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pcb->snd_scale = data;
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if (pcb->snd_scale > 14U) {
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pcb->snd_scale = 14U;
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}
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pcb->rcv_scale = TCP_RCV_SCALE;
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pcb->flags |= TF_WND_SCALE;
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}
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/* Advance to next option */
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c += 0x03;
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break;
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#endif
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#if LWIP_TCP_TIMESTAMPS
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case 0x08:
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case LWIP_TCP_OPT_TS:
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LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_parseopt: TS\n"));
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if (opts[c + 1] != 0x0A || c + 0x0A > max_c) {
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if (tcp_getoptbyte() != LWIP_TCP_OPT_LEN_TS || (tcp_optidx - 2 + LWIP_TCP_OPT_LEN_TS) > max_c) {
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/* Bad length */
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LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_parseopt: bad length\n"));
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return;
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}
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/* TCP timestamp option with valid length */
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tsval = (opts[c+2]) | (opts[c+3] << 8) |
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(opts[c+4] << 16) | (opts[c+5] << 24);
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tsval = tcp_getoptbyte();
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tsval |= (tcp_getoptbyte() << 8);
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tsval |= (tcp_getoptbyte() << 16);
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tsval |= (tcp_getoptbyte() << 24);
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if (flags & TCP_SYN) {
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pcb->ts_recent = ntohl(tsval);
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/* Enable sending timestamps in every segment now that we know
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@ -1702,13 +1740,14 @@ tcp_parseopt(struct tcp_pcb *pcb)
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} else if (TCP_SEQ_BETWEEN(pcb->ts_lastacksent, seqno, seqno+tcplen)) {
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pcb->ts_recent = ntohl(tsval);
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}
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/* Advance to next option */
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c += 0x0A;
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/* Advance to next option (6 bytes already read) */
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tcp_optidx += LWIP_TCP_OPT_LEN_TS - 6;
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break;
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#endif
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default:
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LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_parseopt: other\n"));
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if (opts[c + 1] == 0) {
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data = tcp_getoptbyte();
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if (data < 2) {
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LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_parseopt: bad length\n"));
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/* If the length field is zero, the options are malformed
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and we don't process them further. */
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@ -1716,7 +1755,7 @@ tcp_parseopt(struct tcp_pcb *pcb)
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}
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/* All other options have a length field, so that we easily
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can skip past them. */
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c += opts[c + 1];
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tcp_optidx += data - 2;
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}
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}
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}
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@ -298,22 +298,30 @@ struct tcp_seg {
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struct tcp_hdr *tcphdr; /* the TCP header */
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};
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#define LWIP_TCP_OPT_LEN_MSS 4
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#define LWIP_TCP_OPT_EOL 0
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#define LWIP_TCP_OPT_NOP 1
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#define LWIP_TCP_OPT_MSS 2
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#define LWIP_TCP_OPT_WS 3
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#define LWIP_TCP_OPT_TS 8
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#define LWIP_TCP_OPT_LEN_MSS 4
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#if LWIP_TCP_TIMESTAMPS
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#define LWIP_TCP_OPT_LEN_TS 12
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#define LWIP_TCP_OPT_LEN_TS 10
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#define LWIP_TCP_OPT_LEN_TS_OUT 12 /* aligned for output (includes NOP padding) */
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#else
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#define LWIP_TCP_OPT_LEN_TS 0
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#define LWIP_TCP_OPT_LEN_TS_OUT 0
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#endif
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#if LWIP_WND_SCALE
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#define LWIP_TCP_OPT_LEN_WS 4
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#define LWIP_TCP_OPT_LEN_WS 3
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#define LWIP_TCP_OPT_LEN_WS_OUT 4 /* aligned for output (includes NOP padding) */
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#else
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#define LWIP_TCP_OPT_LEN_WS 0
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#define LWIP_TCP_OPT_LEN_WS_OUT 0
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#endif
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#define LWIP_TCP_OPT_LENGTH(flags) \
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(flags & TF_SEG_OPTS_MSS ? LWIP_TCP_OPT_LEN_MSS : 0) + \
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(flags & TF_SEG_OPTS_TS ? LWIP_TCP_OPT_LEN_TS : 0) + \
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(flags & TF_SEG_OPTS_WND_SCALE ? LWIP_TCP_OPT_LEN_WS : 0)
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(flags & TF_SEG_OPTS_MSS ? LWIP_TCP_OPT_LEN_MSS : 0) + \
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(flags & TF_SEG_OPTS_TS ? LWIP_TCP_OPT_LEN_TS_OUT : 0) + \
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(flags & TF_SEG_OPTS_WND_SCALE ? LWIP_TCP_OPT_LEN_WS_OUT : 0)
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/** This returns a TCP header option for MSS in an u32_t */
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#define TCP_BUILD_MSS_OPTION(mss) htonl(0x02040000 | ((mss) & 0xFFFF))
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