1 files changed, 48 insertions, 0 deletions
diff --git a/package/systemd/0003-resolved-do-not-allocate-packets-with-minimum-size.patch b/package/systemd/0003-resolved-do-not-allocate-packets-with-minimum-size.patch
new file mode 100644
index 0000000000..750911383c
--- /dev/null
+++ b/package/systemd/0003-resolved-do-not-allocate-packets-with-minimum-size.patch
@@ -0,0 +1,48 @@
+From 88795538726a5bbfd9efc13d441cb05e1d7fc139 Mon Sep 17 00:00:00 2001
+From: =?UTF-8?q?Zbigniew=20J=C4=99drzejewski-Szmek?= <zbyszek@in.waw.pl>
+Date: Tue, 27 Jun 2017 14:20:00 -0400
+Subject: [PATCH] resolved: do not allocate packets with minimum size
+
+dns_packet_new() is sometimes called with mtu == 0, and in that case we should
+allocate more than the absolute minimum (which is the dns packet header size),
+otherwise we have to resize immediately again after appending the first data to
+the packet.
+
+This partially reverts the previous commit.
+
+[Upstream commit: https://github.com/systemd/systemd/commit/88795538726a5bbfd9efc13d441cb05e1d7fc139]
+Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
+---
+ src/resolve/resolved-dns-packet.c | 12 +++++++++++-
+ 1 file changed, 11 insertions(+), 1 deletion(-)
+
+diff --git a/src/resolve/resolved-dns-packet.c b/src/resolve/resolved-dns-packet.c
+index 821b66e266..d1f0f760a4 100644
+--- a/src/resolve/resolved-dns-packet.c
++++ b/src/resolve/resolved-dns-packet.c
+@@ -28,6 +28,9 @@
+ 
+ #define EDNS0_OPT_DO (1<<15)
+ 
++#define DNS_PACKET_SIZE_START 512
++assert_cc(DNS_PACKET_SIZE_START > UDP_PACKET_HEADER_SIZE)
++
+ typedef struct DnsPacketRewinder {
+         DnsPacket *packet;
+         size_t saved_rindex;
+@@ -47,7 +50,14 @@ int dns_packet_new(DnsPacket **ret, DnsProtocol protocol, size_t mtu) {
+ 
+         assert(ret);
+ 
+-        a = MAX(mtu, DNS_PACKET_HEADER_SIZE);
++        /* When dns_packet_new() is called with mtu == 0, allocate more than the
++         * absolute minimum (which is the dns packet header size), to avoid
++         * resizing immediately again after appending the first data to the packet.
++         */
++        if (mtu < UDP_PACKET_HEADER_SIZE)
++                a = DNS_PACKET_SIZE_START;
++        else
++                a = MAX(mtu, DNS_PACKET_HEADER_SIZE);
+ 
+         /* round up to next page size */
+         a = PAGE_ALIGN(ALIGN(sizeof(DnsPacket)) + a) - ALIGN(sizeof(DnsPacket));