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libsa: re-send ACK for older data packets in tftp

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In current tftp code we drop out-of-order packets; however, we should play
nice and re-send ACK for older data packets we are receiving. This will
hopefully stop server repeating those packets we already have received.
Note we do not answer duplicates from "previous" session (that is, session
with different port number), those will eventually time out.

Differential Revision:	https://reviews.freebsd.org/D17087
This commit is contained in:
Toomas Soome 2018-10-23 13:38:39 +00:00
parent 8796e291f8
commit bb489cd7ad
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=339651
1 changed files with 13 additions and 5 deletions
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18
stand/libsa/tftp.c
View file

@ -163,7 +163,7 @@ tftp_senderr(struct tftp_handle *h, u_short errcode, const char *msg)
}
static void
tftp_sendack(struct tftp_handle *h)
tftp_sendack(struct tftp_handle *h, u_short block)
{
struct {
u_char header[HEADER_SIZE];
@ -173,7 +173,7 @@ tftp_sendack(struct tftp_handle *h)
wbuf.t.th_opcode = htons((u_short) ACK);
wtail = (char *) &wbuf.t.th_block;
wbuf.t.th_block = htons((u_short) h->currblock);
wbuf.t.th_block = htons(block);
wtail += 2;
sendudp(h->iodesc, &wbuf.t, wtail - (char *) &wbuf.t);
@ -205,9 +205,17 @@ recvtftp(struct iodesc *d, void **pkt, void **payload, time_t tleft,
case DATA: {
int got;
if (htons(t->th_block) < (u_short) d->xid) {
/*
* Apparently our ACK was missed, re-send.
*/
tftp_sendack(h, htons(t->th_block));
free(ptr);
return (-1);
}
if (htons(t->th_block) != (u_short) d->xid) {
/*
* Expected block?
* Packet from the future, drop this.
*/
free(ptr);
return (-1);
@ -219,7 +227,7 @@ recvtftp(struct iodesc *d, void **pkt, void **payload, time_t tleft,
struct udphdr *uh;
uh = (struct udphdr *) t - 1;
d->destport = uh->uh_sport;
} /* else check uh_sport has not changed??? */
}
got = len - (t->th_data - (char *)t);
*pkt = ptr;
*payload = t;
@ -364,7 +372,7 @@ tftp_makereq(struct tftp_handle *h)
h->islastblock = 0;
if (res < h->tftp_blksize) {
h->islastblock = 1; /* very short file */
tftp_sendack(h);
tftp_sendack(h, h->currblock);
}
return (0);
}