Fix a regression in the TCP handling of received segments.
When receiving TCP segments the stack protects itself by limiting the resources allocated for a TCP connections. This patch adds an exception to these limitations for the TCP segement which is the next expected in-sequence segment. Without this patch, TCP connections may stall and finally fail in some cases of packet loss. Reported by: jhb@ Reviewed by: jtl@, rrs@ MFC after: 3 days Sponsored by: Netflix, Inc. Differential Revision: https://reviews.freebsd.org/D18580
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Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=342280
@ -579,7 +579,8 @@ tcp_reass(struct tcpcb *tp, struct tcphdr *th, tcp_seq *seq_start,
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*/
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lenofoh = tcp_reass_overhead_of_chain(m, &mlast);
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sb = &tp->t_inpcb->inp_socket->so_rcv;
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if ((sb->sb_mbcnt + tp->t_segqmbuflen + lenofoh) > sb->sb_mbmax) {
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if ((th->th_seq != tp->rcv_nxt || !TCPS_HAVEESTABLISHED(tp->t_state)) &&
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(sb->sb_mbcnt + tp->t_segqmbuflen + lenofoh) > sb->sb_mbmax) {
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/* No room */
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TCPSTAT_INC(tcps_rcvreassfull);
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#ifdef TCP_REASS_COUNTERS
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@ -588,6 +589,11 @@ tcp_reass(struct tcpcb *tp, struct tcphdr *th, tcp_seq *seq_start,
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#ifdef TCP_REASS_LOGGING
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tcp_log_reassm(tp, NULL, NULL, th->th_seq, lenofoh, TCP_R_LOG_LIMIT_REACHED, 0);
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#endif
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if ((s = tcp_log_addrs(&tp->t_inpcb->inp_inc, th, NULL, NULL))) {
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log(LOG_DEBUG, "%s; %s: mbuf count limit reached, "
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"segment dropped\n", s, __func__);
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free(s, M_TCPLOG);
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}
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m_freem(m);
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*tlenp = 0;
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#ifdef TCP_REASS_LOGGING
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@ -936,6 +942,20 @@ tcp_reass(struct tcpcb *tp, struct tcphdr *th, tcp_seq *seq_start,
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* is understood.
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*/
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new_entry:
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if (th->th_seq == tp->rcv_nxt && TCPS_HAVEESTABLISHED(tp->t_state)) {
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tp->rcv_nxt += *tlenp;
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flags = th->th_flags & TH_FIN;
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TCPSTAT_INC(tcps_rcvoopack);
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TCPSTAT_ADD(tcps_rcvoobyte, *tlenp);
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SOCKBUF_LOCK(&so->so_rcv);
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if (so->so_rcv.sb_state & SBS_CANTRCVMORE) {
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m_freem(m);
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} else {
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sbappendstream_locked(&so->so_rcv, m, 0);
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}
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sorwakeup_locked(so);
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return (flags);
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}
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if (tcp_new_limits) {
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if ((tp->t_segqlen > tcp_reass_queue_guard) &&
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(*tlenp < MSIZE)) {
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@ -960,9 +980,7 @@ tcp_reass(struct tcpcb *tp, struct tcphdr *th, tcp_seq *seq_start,
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return (0);
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}
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} else {
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if ((th->th_seq != tp->rcv_nxt || !TCPS_HAVEESTABLISHED(tp->t_state)) &&
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tp->t_segqlen >= min((so->so_rcv.sb_hiwat / tp->t_maxseg) + 1,
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if (tp->t_segqlen >= min((so->so_rcv.sb_hiwat / tp->t_maxseg) + 1,
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tcp_reass_maxqueuelen)) {
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TCPSTAT_INC(tcps_rcvreassfull);
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*tlenp = 0;
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