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Send TCP DNS messages in one write() call. Stops TCP stream fragmenting.

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This is an optimisation, not a bugfix. Thanks to Jim Bos for spotting it.
This commit is contained in:
Simon Kelley
2013-04-22 10:18:26 +01:00
parent 2b6390fdc9
commit 4b5ea12e90
1 changed files with 13 additions and 18 deletions
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31
src/forward.c
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@@ -880,9 +880,12 @@ unsigned char *tcp_request(int confd, time_t now,
unsigned short qtype;
unsigned int gotname;
unsigned char c1, c2;
/* Max TCP packet + slop */
unsigned char *packet = whine_malloc(65536 + MAXDNAME + RRFIXEDSZ);
struct dns_header *header;
/* Max TCP packet + slop + size */
unsigned char *packet = whine_malloc(65536 + MAXDNAME + RRFIXEDSZ + sizeof(u16));
unsigned char *payload = &packet[2];
/* largest field in header is 16-bits, so this is still sufficiently aligned */
struct dns_header *header = (struct dns_header *)payload;
u16 *length = (u16 *)packet;
struct server *last_server;
struct in_addr dst_addr_4;
union mysockaddr peer_addr;
@@ -896,14 +899,12 @@ unsigned char *tcp_request(int confd, time_t now,
if (!packet ||
!read_write(confd, &c1, 1, 1) || !read_write(confd, &c2, 1, 1) ||
!(size = c1 << 8 | c2) ||
!read_write(confd, packet, size, 1))
!read_write(confd, payload, size, 1))
return packet;
if (size < (int)sizeof(struct dns_header))
continue;
header = (struct dns_header *)packet;
/* save state of "cd" flag in query */
checking_disabled = header->hb4 & HB4_CD;
@@ -1020,12 +1021,9 @@ unsigned char *tcp_request(int confd, time_t now,
#endif
}
c1 = size >> 8;
c2 = size;
*length = htons(size);
if (!read_write(last_server->tcpfd, &c1, 1, 0) ||
!read_write(last_server->tcpfd, &c2, 1, 0) ||
!read_write(last_server->tcpfd, packet, size, 0) ||
if (!read_write(last_server->tcpfd, packet, size + sizeof(u16), 0) ||
!read_write(last_server->tcpfd, &c1, 1, 1) ||
!read_write(last_server->tcpfd, &c2, 1, 1))
{
@@ -1035,7 +1033,7 @@ unsigned char *tcp_request(int confd, time_t now,
}
m = (c1 << 8) | c2;
if (!read_write(last_server->tcpfd, packet, m, 1))
if (!read_write(last_server->tcpfd, payload, m, 1))
return packet;
if (!gotname)
@@ -1071,12 +1069,9 @@ unsigned char *tcp_request(int confd, time_t now,
check_log_writer(NULL);
c1 = m>>8;
c2 = m;
if (m == 0 ||
!read_write(confd, &c1, 1, 0) ||
!read_write(confd, &c2, 1, 0) ||
!read_write(confd, packet, m, 0))
*length = htons(m);
if (m == 0 || !read_write(confd, packet, m + sizeof(u16), 0))
return packet;
}
}