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From 4b5ea12e90024ade5033b3b83a8b2620035952ba Mon Sep 17 00:00:00 2001
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From: Simon Kelley <simon@thekelleys.org.uk>
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Date: Mon, 22 Apr 2013 10:18:26 +0100
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Subject: [PATCH] Send TCP DNS messages in one write() call. Stops TCP stream
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fragmenting.
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This is an optimisation, not a bugfix. Thanks to Jim Bos for spotting it.
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---
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src/forward.c | 31 +++++++++++++------------------
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1 file changed, 13 insertions(+), 18 deletions(-)
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diff --git a/src/forward.c b/src/forward.c
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index 1ea25dd..77d6849 100644
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--- a/src/forward.c
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+++ b/src/forward.c
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@@ -880,9 +880,12 @@ unsigned char *tcp_request(int confd, time_t now,
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unsigned short qtype;
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unsigned int gotname;
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unsigned char c1, c2;
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- /* Max TCP packet + slop */
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- unsigned char *packet = whine_malloc(65536 + MAXDNAME + RRFIXEDSZ);
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- struct dns_header *header;
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+ /* Max TCP packet + slop + size */
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+ unsigned char *packet = whine_malloc(65536 + MAXDNAME + RRFIXEDSZ + sizeof(u16));
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+ unsigned char *payload = &packet[2];
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+ /* largest field in header is 16-bits, so this is still sufficiently aligned */
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+ struct dns_header *header = (struct dns_header *)payload;
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+ u16 *length = (u16 *)packet;
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struct server *last_server;
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struct in_addr dst_addr_4;
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union mysockaddr peer_addr;
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@@ -896,14 +899,12 @@ unsigned char *tcp_request(int confd, time_t now,
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if (!packet ||
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!read_write(confd, &c1, 1, 1) || !read_write(confd, &c2, 1, 1) ||
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!(size = c1 << 8 | c2) ||
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- !read_write(confd, packet, size, 1))
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+ !read_write(confd, payload, size, 1))
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return packet;
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if (size < (int)sizeof(struct dns_header))
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continue;
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- header = (struct dns_header *)packet;
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-
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/* save state of "cd" flag in query */
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checking_disabled = header->hb4 & HB4_CD;
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@@ -1020,12 +1021,9 @@ unsigned char *tcp_request(int confd, time_t now,
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#endif
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}
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- c1 = size >> 8;
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- c2 = size;
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+ *length = htons(size);
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- if (!read_write(last_server->tcpfd, &c1, 1, 0) ||
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- !read_write(last_server->tcpfd, &c2, 1, 0) ||
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- !read_write(last_server->tcpfd, packet, size, 0) ||
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+ if (!read_write(last_server->tcpfd, packet, size + sizeof(u16), 0) ||
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!read_write(last_server->tcpfd, &c1, 1, 1) ||
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!read_write(last_server->tcpfd, &c2, 1, 1))
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{
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@@ -1035,7 +1033,7 @@ unsigned char *tcp_request(int confd, time_t now,
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}
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m = (c1 << 8) | c2;
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- if (!read_write(last_server->tcpfd, packet, m, 1))
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+ if (!read_write(last_server->tcpfd, payload, m, 1))
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return packet;
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if (!gotname)
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@@ -1071,12 +1069,9 @@ unsigned char *tcp_request(int confd, time_t now,
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check_log_writer(NULL);
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- c1 = m>>8;
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- c2 = m;
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- if (m == 0 ||
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- !read_write(confd, &c1, 1, 0) ||
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- !read_write(confd, &c2, 1, 0) ||
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- !read_write(confd, packet, m, 0))
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+ *length = htons(m);
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+
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+ if (m == 0 || !read_write(confd, packet, m + sizeof(u16), 0))
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return packet;
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}
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}
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--
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1.8.1.4
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