Add SA-15:13.tcp.
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Xin LI
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svn2git
2020-12-08 03:00:23 +00:00
svn path=/head/; revision=47036
6 changed files with 269 additions and 0 deletions
165
share/security/advisories/FreeBSD-SA-15:13.tcp.asc
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165
share/security/advisories/FreeBSD-SA-15:13.tcp.asc
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-----BEGIN PGP SIGNED MESSAGE-----
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Hash: SHA512
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=============================================================================
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FreeBSD-SA-15:13.tcp Security Advisory
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The FreeBSD Project
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Topic: Resource exhaustion due to sessions stuck in LAST_ACK state
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Category: core
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Module: inet
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Announced: 2015-07-21
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Credits: Lawrence Stewart (Netflix, Inc.),
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Jonathan Looney (Juniper SIRT)
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Affects: All supported versions of FreeBSD.
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Corrected: 2015-07-21 23:42:17 UTC (stable/10, 10.2-PRERELEASE)
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2015-07-21 23:42:17 UTC (stable/10, 10.2-BETA1-p1)
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2015-07-21 23:42:17 UTC (stable/10, 10.2-BETA2-p1)
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2015-07-21 23:42:56 UTC (releng/10.1, 10.1-RELEASE-p15)
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2015-07-21 23:42:20 UTC (stable/9, 9.3-STABLE)
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2015-07-21 23:42:56 UTC (releng/9.3, 9.3-RELEASE-p20)
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2015-07-21 23:42:20 UTC (stable/8, 8.4-STABLE)
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2015-07-21 23:42:56 UTC (releng/8.4, 8.4-RELEASE-p34)
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CVE Name: CVE-2015-5358
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For general information regarding FreeBSD Security Advisories,
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including descriptions of the fields above, security branches, and the
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following sections, please visit <URL:https://security.FreeBSD.org/>.
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I. Background
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The Transmission Control Protocol (TCP) of the TCP/IP protocol suite
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provides a connection-oriented, reliable, sequence-preserving data
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stream service.
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A socket enters the LAST_ACK state when the local process closes its socket
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after a FIN has already been received from the remote peer. The socket
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will remain in the LAST_ACK state until the kernel has transmitted a FIN to
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the remote peer and the kernel has received an acknowledgement of that FIN
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from the remote peer, or all retransmits of the FIN have failed and the
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connection times out.
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II. Problem Description
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TCP connections transitioning to the LAST_ACK state can become permanently
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stuck due to mishandling of protocol state in certain situations, which in
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turn can lead to accumulated consumption and eventual exhaustion of system
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resources, such as mbufs and sockets.
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III. Impact
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An attacker who can repeatedly establish TCP connections to a victim system
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(for instance, a Web server) could create many TCP connections that are
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stuck in LAST_ACK state and cause resource exhaustion, resulting in a
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denial of service condition. This may also happen in normal operation
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where no intentional attack is conducted, but an attacker who can send
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specifically crafted packets can trigger this more reliably.
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IV. Workaround
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No workaround is available, but systems that do not provide TCP based
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service to untrusted networks are not vulnerable.
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Note that the tcpdrop(8) utility can be used to purge connections which
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have become wedged. For example, the following command can be used to
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generate commands that would drop all connections whose last rcvtime is
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more than 100s:
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netstat -nxp tcp | \
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awk '{ if (int($NF) > 100) print "tcpdrop " $4 " " $5 }'
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The system administrator can then run the generated script as a temporary
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measure. Please refer to the tcpdump(8) manual page for additional
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information.
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V. Solution
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Perform one of the following:
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1) Upgrade your vulnerable system to a supported FreeBSD stable or
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release / security branch (releng) dated after the correction date.
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2) To update your vulnerable system via a binary patch:
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Systems running a RELEASE version of FreeBSD on the i386 or amd64
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platforms can be updated via the freebsd-update(8) utility:
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# freebsd-update fetch
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# freebsd-update install
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3) To update your vulnerable system via a source code patch:
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The following patches have been verified to apply to the applicable
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FreeBSD release branches.
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a) Download the relevant patch from the location below, and verify the
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detached PGP signature using your PGP utility.
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[FreeBSD 10.1]
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# fetch https://security.FreeBSD.org/patches/SA-15:13/tcp.patch
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# fetch https://security.FreeBSD.org/patches/SA-15:13/tcp.patch.asc
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# gpg --verify tcp.patch.asc
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[FreeBSD 9.x and 8.x]
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# fetch https://security.FreeBSD.org/patches/SA-15:13/tcp-9.patch
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# fetch https://security.FreeBSD.org/patches/SA-15:13/tcp-9.patch.asc
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# gpg --verify tcp-9.patch.asc
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b) Apply the patch. Execute the following commands as root:
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# cd /usr/src
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# patch < /path/to/patch
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c) Recompile your kernel as described in
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<URL:https://www.FreeBSD.org/handbook/kernelconfig.html> and reboot the
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system.
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VI. Correction details
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The following list contains the correction revision numbers for each
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affected branch.
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Branch/path Revision
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- -------------------------------------------------------------------------
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stable/8/ r285779
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releng/8.4/ r285780
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stable/9/ r285779
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releng/9.3/ r285780
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stable/10/ r285778
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releng/10.1/ r285780
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- -------------------------------------------------------------------------
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To see which files were modified by a particular revision, run the
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following command, replacing NNNNNN with the revision number, on a
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machine with Subversion installed:
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# svn diff -cNNNNNN --summarize svn://svn.freebsd.org/base
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Or visit the following URL, replacing NNNNNN with the revision number:
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<URL:https://svnweb.freebsd.org/base?view=revision&revision=NNNNNN>
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VII. References
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<URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2015-5358>
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The latest revision of this advisory is available at
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<URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-15:13.tcp.asc>
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-----BEGIN PGP SIGNATURE-----
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canMZYhLMD6A1x5T54Ya
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=UPeI
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-----END PGP SIGNATURE-----
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31
share/security/patches/SA-15:13/tcp-9.patch
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31
share/security/patches/SA-15:13/tcp-9.patch
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@ -0,0 +1,31 @@
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Index: sys/netinet/tcp_output.c
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===================================================================
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--- sys/netinet/tcp_output.c (revision 285435)
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+++ sys/netinet/tcp_output.c (working copy)
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@@ -397,7 +397,7 @@ after_sack_rexmit:
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flags &= ~TH_FIN;
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}
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- if (len < 0) {
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+ if (len <= 0) {
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/*
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* If FIN has been sent but not acked,
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* but we haven't been called to retransmit,
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@@ -407,9 +407,16 @@ after_sack_rexmit:
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* to (closed) window, and set the persist timer
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* if it isn't already going. If the window didn't
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* close completely, just wait for an ACK.
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+ *
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+ * We also do a general check here to ensure that
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+ * we will set the persist timer when we have data
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+ * to send, but a 0-byte window. This makes sure
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+ * the persist timer is set even if the packet
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+ * hits one of the "goto send" lines below.
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*/
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len = 0;
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- if (sendwin == 0) {
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+ if ((sendwin == 0) && (TCPS_HAVEESTABLISHED(tp->t_state)) &&
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+ (off < (int) so->so_snd.sb_cc)) {
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tcp_timer_activate(tp, TT_REXMT, 0);
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tp->t_rxtshift = 0;
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tp->snd_nxt = tp->snd_una;
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17
share/security/patches/SA-15:13/tcp-9.patch.asc
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17
share/security/patches/SA-15:13/tcp-9.patch.asc
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@ -0,0 +1,17 @@
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-----BEGIN PGP SIGNATURE-----
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Version: GnuPG v2.1.6 (FreeBSD)
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AiZDOe38k8NCOFahQtio
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=CFEV
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-----END PGP SIGNATURE-----
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31
share/security/patches/SA-15:13/tcp.patch
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31
share/security/patches/SA-15:13/tcp.patch
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@ -0,0 +1,31 @@
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Index: sys/netinet/tcp_output.c
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===================================================================
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--- sys/netinet/tcp_output.c (revision 285435)
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+++ sys/netinet/tcp_output.c (working copy)
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@@ -400,7 +400,7 @@ after_sack_rexmit:
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flags &= ~TH_FIN;
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}
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- if (len < 0) {
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+ if (len <= 0) {
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/*
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* If FIN has been sent but not acked,
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* but we haven't been called to retransmit,
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@@ -410,9 +410,16 @@ after_sack_rexmit:
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* to (closed) window, and set the persist timer
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* if it isn't already going. If the window didn't
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* close completely, just wait for an ACK.
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+ *
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+ * We also do a general check here to ensure that
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+ * we will set the persist timer when we have data
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+ * to send, but a 0-byte window. This makes sure
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+ * the persist timer is set even if the packet
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+ * hits one of the "goto send" lines below.
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*/
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len = 0;
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- if (sendwin == 0) {
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+ if ((sendwin == 0) && (TCPS_HAVEESTABLISHED(tp->t_state)) &&
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+ (off < (int) so->so_snd.sb_cc)) {
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tcp_timer_activate(tp, TT_REXMT, 0);
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tp->t_rxtshift = 0;
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tp->snd_nxt = tp->snd_una;
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17
share/security/patches/SA-15:13/tcp.patch.asc
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17
share/security/patches/SA-15:13/tcp.patch.asc
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@ -0,0 +1,17 @@
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-----BEGIN PGP SIGNATURE-----
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|
Version: GnuPG v2.1.6 (FreeBSD)
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=WBT+
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-----END PGP SIGNATURE-----
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@ -10,6 +10,14 @@
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<month>
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<month>
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<name>7</name>
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<name>7</name>
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<day>
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<name>21</name>
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<advisory>
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<name>FreeBSD-SA-15:13.tcp</name>
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</advisory>
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</day>
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<day>
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<day>
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<name>9</name>
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<name>9</name>
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Reference in a new issue