Module Name: src
Committed By: maxv
Date: Thu Mar 29 17:46:17 UTC 2018
Modified Files:
src/sys/netinet: tcp_input.c
Log Message:
Reorder/Fix comments to clarify.
To generate a diff of this commit:
cvs rdiff -u -r1.398 -r1.399 src/sys/netinet/tcp_input.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/netinet/tcp_input.c
diff -u src/sys/netinet/tcp_input.c:1.398 src/sys/netinet/tcp_input.c:1.399
--- src/sys/netinet/tcp_input.c:1.398 Thu Mar 29 17:12:36 2018
+++ src/sys/netinet/tcp_input.c Thu Mar 29 17:46:17 2018
@@ -1,4 +1,4 @@
-/* $NetBSD: tcp_input.c,v 1.398 2018/03/29 17:12:36 maxv Exp $ */
+/* $NetBSD: tcp_input.c,v 1.399 2018/03/29 17:46:17 maxv Exp $ */
/*
* Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
@@ -148,7 +148,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: tcp_input.c,v 1.398 2018/03/29 17:12:36 maxv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: tcp_input.c,v 1.399 2018/03/29 17:46:17 maxv Exp $");
#ifdef _KERNEL_OPT
#include "opt_inet.h"
@@ -444,6 +444,11 @@ tcpipqent_free(struct ipqent *ipqe)
splx(s);
}
+/*
+ * Insert segment ti into reassembly queue of tcp with
+ * control block tp. Return TH_FIN if reassembly now includes
+ * a segment with FIN.
+ */
static int
tcp_reass(struct tcpcb *tp, const struct tcphdr *th, struct mbuf *m, int tlen)
{
@@ -479,8 +484,8 @@ tcp_reass(struct tcpcb *tp, const struct
rcvoobyte = tlen;
/*
- * Copy these to local variables because the tcpiphdr
- * gets munged while we are collapsing mbufs.
+ * Copy these to local variables because the TCP header gets munged
+ * while we are collapsing mbufs.
*/
pkt_seq = th->th_seq;
pkt_len = tlen;
@@ -547,6 +552,7 @@ tcp_reass(struct tcpcb *tp, const struct
#ifdef TCP_REASS_COUNTERS
count++;
#endif
+
/*
* If the received segment is just right after this
* fragment, merge the two together and then check
@@ -567,14 +573,16 @@ tcp_reass(struct tcpcb *tp, const struct
TCP_REASS_COUNTER_INCR(&tcp_reass_append);
goto free_ipqe;
}
+
/*
* If the received segment is completely past this
- * fragment, we need to go the next fragment.
+ * fragment, we need to go to the next fragment.
*/
if (SEQ_LT(q->ipqe_seq + q->ipqe_len, pkt_seq)) {
p = q;
continue;
}
+
/*
* If the fragment is past the received segment,
* it (or any following) can't be concatenated.
@@ -586,7 +594,7 @@ tcp_reass(struct tcpcb *tp, const struct
/*
* We've received all the data in this segment before.
- * mark it as a duplicate and return.
+ * Mark it as a duplicate and return.
*/
if (SEQ_LEQ(q->ipqe_seq, pkt_seq) &&
SEQ_GEQ(q->ipqe_seq + q->ipqe_len, pkt_seq + pkt_len)) {
@@ -602,6 +610,7 @@ tcp_reass(struct tcpcb *tp, const struct
TCP_REASS_COUNTER_INCR(&tcp_reass_segdup);
goto out;
}
+
/*
* Received segment completely overlaps this fragment
* so we drop the fragment (this keeps the temporal
@@ -614,11 +623,11 @@ tcp_reass(struct tcpcb *tp, const struct
TCP_REASS_COUNTER_INCR(&tcp_reass_fragdup);
goto free_ipqe;
}
+
/*
- * RX'ed segment extends past the end of the
- * fragment. Drop the overlapping bytes. Then
- * merge the fragment and segment then treat as
- * a longer received packet.
+ * Received segment extends past the end of the fragment.
+ * Drop the overlapping bytes, merge the fragment and
+ * segment, and treat as a longer received packet.
*/
if (SEQ_LT(q->ipqe_seq, pkt_seq) &&
SEQ_GT(q->ipqe_seq + q->ipqe_len, pkt_seq)) {
@@ -639,11 +648,12 @@ tcp_reass(struct tcpcb *tp, const struct
TCP_REASS_COUNTER_INCR(&tcp_reass_overlaptail);
goto free_ipqe;
}
+
/*
- * RX'ed segment extends past the front of the
- * fragment. Drop the overlapping bytes on the
- * received packet. The packet will then be
- * contatentated with this fragment a bit later.
+ * Received segment extends past the front of the fragment.
+ * Drop the overlapping bytes on the received packet. The
+ * packet will then be concatenated with this fragment a
+ * bit later.
*/
if (SEQ_GT(q->ipqe_seq, pkt_seq) &&
SEQ_LT(q->ipqe_seq, pkt_seq + pkt_len)) {
@@ -659,8 +669,9 @@ tcp_reass(struct tcpcb *tp, const struct
TCP_REASS_COUNTER_INCR(&tcp_reass_overlapfront);
rcvoobyte -= overlap;
}
+
/*
- * If the received segment immediates precedes this
+ * If the received segment immediately precedes this
* fragment then tack the fragment onto this segment
* and reinsert the data.
*/
@@ -688,11 +699,12 @@ tcp_reass(struct tcpcb *tp, const struct
TCP_REASS_COUNTER_INCR(&tcp_reass_prepend);
break;
}
+
/*
* If the fragment is before the segment, remember it.
* When this loop is terminated, p will contain the
- * pointer to fragment that is right before the received
- * segment.
+ * pointer to the fragment that is right before the
+ * received segment.
*/
if (SEQ_LEQ(q->ipqe_seq, pkt_seq))
p = q;
@@ -724,14 +736,13 @@ tcp_reass(struct tcpcb *tp, const struct
TCP_REASS_COUNTER_INCR(&tcp_reass_iteration[count]);
#endif
- insert_it:
-
+insert_it:
/*
- * Allocate a new queue entry since the received segment did not
- * collapse onto any other out-of-order block; thus we are allocating
- * a new block. If it had collapsed, tiqe would not be NULL and
- * we would be reusing it.
- * XXX If we can't, just drop the packet. XXX
+ * Allocate a new queue entry (block) since the received segment
+ * did not collapse onto any other out-of-order block. If it had
+ * collapsed, tiqe would not be NULL and we would be reusing it.
+ *
+ * If the allocation fails, drop the packet.
*/
if (tiqe == NULL) {
tiqe = tcpipqent_alloc();
@@ -781,7 +792,6 @@ tcp_reass(struct tcpcb *tp, const struct
tp->t_segqlen++;
skip_replacement:
-
TAILQ_INSERT_HEAD(&tp->timeq, tiqe, ipqe_timeq);
present:
@@ -814,10 +824,11 @@ present:
tcpipqent_free(q);
TCP_REASS_UNLOCK(tp);
sorwakeup(so);
- return (pkt_flags);
+ return pkt_flags;
+
out:
TCP_REASS_UNLOCK(tp);
- return (0);
+ return 0;
}
#ifdef INET6
@@ -2300,7 +2311,7 @@ after_listen:
TCP_STAT_PUTREF();
}
tcp_new_dsack(tp, th->th_seq, todrop);
- hdroptlen += todrop; /* drop from head afterwards */
+ hdroptlen += todrop; /* drop from head afterwards (m_adj) */
th->th_seq += todrop;
tlen -= todrop;
tcp_urp_drop(th, todrop, &tiflags);
@@ -2795,18 +2806,16 @@ dodata:
if ((tlen || (tiflags & TH_FIN)) &&
TCPS_HAVERCVDFIN(tp->t_state) == 0) {
/*
- * Insert segment ti into reassembly queue of tcp with
- * control block tp. Return TH_FIN if reassembly now includes
- * a segment with FIN. The macro form does the common case
- * inline (segment is the next to be received on an
- * established connection, and the queue is empty),
- * avoiding linkage into and removal from the queue and
- * repetition of various conversions.
- * Set DELACK for segments received in order, but ack
- * immediately when segments are out of order
- * (so fast retransmit can work).
+ * Handle the common case:
+ * o Segment is the next to be received, and
+ * o The queue is empty, and
+ * o The connection is established
+ * In this case, we avoid calling tcp_reass.
+ *
+ * tcp_setup_ack: set DELACK for segments received in order,
+ * but ack immediately when segments are out of order (so that
+ * fast retransmit can work).
*/
- /* NOTE: this was TCP_REASS() macro, but used only once */
TCP_REASS_LOCK(tp);
if (th->th_seq == tp->rcv_nxt &&
TAILQ_FIRST(&tp->segq) == NULL &&
