Initial commit

13 files changed, 827 insertions, 0 deletions

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..a63eff4
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,6 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+# SPDX-FileCopyrightText: 2020 Alyssa Ross <hi@alyssa.is>
+
+*.o
+vsockclient
+vsockserver
diff --git a/LICENSES/GPL-2.0-or-later.txt b/LICENSES/GPL-2.0-or-later.txt
new file mode 100644
index 0000000..1d80ac3
--- /dev/null
+++ b/LICENSES/GPL-2.0-or-later.txt
@@ -0,0 +1,319 @@
+GNU GENERAL PUBLIC LICENSE
+
+Version 2, June 1991
+
+Copyright (C) 1989, 1991 Free Software Foundation, Inc. 
+
+51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
+
+Everyone is permitted to copy and distribute verbatim copies of this license
+document, but changing it is not allowed.
+
+Preamble
+
+The licenses for most software are designed to take away your freedom to share
+and change it. By contrast, the GNU General Public License is intended to
+guarantee your freedom to share and change free software--to make sure the
+software is free for all its users. This General Public License applies to
+most of the Free Software Foundation's software and to any other program whose
+authors commit to using it. (Some other Free Software Foundation software
+is covered by the GNU Lesser General Public License instead.) You can apply
+it to your programs, too.
+
+When we speak of free software, we are referring to freedom, not price. Our
+General Public Licenses are designed to make sure that you have the freedom
+to distribute copies of free software (and charge for this service if you
+wish), that you receive source code or can get it if you want it, that you
+can change the software or use pieces of it in new free programs; and that
+you know you can do these things.
+
+To protect your rights, we need to make restrictions that forbid anyone to
+deny you these rights or to ask you to surrender the rights. These restrictions
+translate to certain responsibilities for you if you distribute copies of
+the software, or if you modify it.
+
+For example, if you distribute copies of such a program, whether gratis or
+for a fee, you must give the recipients all the rights that you have. You
+must make sure that they, too, receive or can get the source code. And you
+must show them these terms so they know their rights.
+
+We protect your rights with two steps: (1) copyright the software, and (2)
+offer you this license which gives you legal permission to copy, distribute
+and/or modify the software.
+
+Also, for each author's protection and ours, we want to make certain that
+everyone understands that there is no warranty for this free software. If
+the software is modified by someone else and passed on, we want its recipients
+to know that what they have is not the original, so that any problems introduced
+by others will not reflect on the original authors' reputations.
+
+Finally, any free program is threatened constantly by software patents. We
+wish to avoid the danger that redistributors of a free program will individually
+obtain patent licenses, in effect making the program proprietary. To prevent
+this, we have made it clear that any patent must be licensed for everyone's
+free use or not licensed at all.
+
+The precise terms and conditions for copying, distribution and modification
+follow.
+
+TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
+
+0. This License applies to any program or other work which contains a notice
+placed by the copyright holder saying it may be distributed under the terms
+of this General Public License. The "Program", below, refers to any such program
+or work, and a "work based on the Program" means either the Program or any
+derivative work under copyright law: that is to say, a work containing the
+Program or a portion of it, either verbatim or with modifications and/or translated
+into another language. (Hereinafter, translation is included without limitation
+in the term "modification".) Each licensee is addressed as "you".
+
+Activities other than copying, distribution and modification are not covered
+by this License; they are outside its scope. The act of running the Program
+is not restricted, and the output from the Program is covered only if its
+contents constitute a work based on the Program (independent of having been
+made by running the Program). Whether that is true depends on what the Program
+does.
+
+1. You may copy and distribute verbatim copies of the Program's source code
+as you receive it, in any medium, provided that you conspicuously and appropriately
+publish on each copy an appropriate copyright notice and disclaimer of warranty;
+keep intact all the notices that refer to this License and to the absence
+of any warranty; and give any other recipients of the Program a copy of this
+License along with the Program.
+
+You may charge a fee for the physical act of transferring a copy, and you
+may at your option offer warranty protection in exchange for a fee.
+
+2. You may modify your copy or copies of the Program or any portion of it,
+thus forming a work based on the Program, and copy and distribute such modifications
+or work under the terms of Section 1 above, provided that you also meet all
+of these conditions:
+
+a) You must cause the modified files to carry prominent notices stating that
+you changed the files and the date of any change.
+
+b) You must cause any work that you distribute or publish, that in whole or
+in part contains or is derived from the Program or any part thereof, to be
+licensed as a whole at no charge to all third parties under the terms of this
+License.
+
+c) If the modified program normally reads commands interactively when run,
+you must cause it, when started running for such interactive use in the most
+ordinary way, to print or display an announcement including an appropriate
+copyright notice and a notice that there is no warranty (or else, saying that
+you provide a warranty) and that users may redistribute the program under
+these conditions, and telling the user how to view a copy of this License.
+(Exception: if the Program itself is interactive but does not normally print
+such an announcement, your work based on the Program is not required to print
+an announcement.)
+
+These requirements apply to the modified work as a whole. If identifiable
+sections of that work are not derived from the Program, and can be reasonably
+considered independent and separate works in themselves, then this License,
+and its terms, do not apply to those sections when you distribute them as
+separate works. But when you distribute the same sections as part of a whole
+which is a work based on the Program, the distribution of the whole must be
+on the terms of this License, whose permissions for other licensees extend
+to the entire whole, and thus to each and every part regardless of who wrote
+it.
+
+Thus, it is not the intent of this section to claim rights or contest your
+rights to work written entirely by you; rather, the intent is to exercise
+the right to control the distribution of derivative or collective works based
+on the Program.
+
+In addition, mere aggregation of another work not based on the Program with
+the Program (or with a work based on the Program) on a volume of a storage
+or distribution medium does not bring the other work under the scope of this
+License.
+
+3. You may copy and distribute the Program (or a work based on it, under Section
+2) in object code or executable form under the terms of Sections 1 and 2 above
+provided that you also do one of the following:
+
+a) Accompany it with the complete corresponding machine-readable source code,
+which must be distributed under the terms of Sections 1 and 2 above on a medium
+customarily used for software interchange; or,
+
+b) Accompany it with a written offer, valid for at least three years, to give
+any third party, for a charge no more than your cost of physically performing
+source distribution, a complete machine-readable copy of the corresponding
+source code, to be distributed under the terms of Sections 1 and 2 above on
+a medium customarily used for software interchange; or,
+
+c) Accompany it with the information you received as to the offer to distribute
+corresponding source code. (This alternative is allowed only for noncommercial
+distribution and only if you received the program in object code or executable
+form with such an offer, in accord with Subsection b above.)
+
+The source code for a work means the preferred form of the work for making
+modifications to it. For an executable work, complete source code means all
+the source code for all modules it contains, plus any associated interface
+definition files, plus the scripts used to control compilation and installation
+of the executable. However, as a special exception, the source code distributed
+need not include anything that is normally distributed (in either source or
+binary form) with the major components (compiler, kernel, and so on) of the
+operating system on which the executable runs, unless that component itself
+accompanies the executable.
+
+If distribution of executable or object code is made by offering access to
+copy from a designated place, then offering equivalent access to copy the
+source code from the same place counts as distribution of the source code,
+even though third parties are not compelled to copy the source along with
+the object code.
+
+4. You may not copy, modify, sublicense, or distribute the Program except
+as expressly provided under this License. Any attempt otherwise to copy, modify,
+sublicense or distribute the Program is void, and will automatically terminate
+your rights under this License. However, parties who have received copies,
+or rights, from you under this License will not have their licenses terminated
+so long as such parties remain in full compliance.
+
+5. You are not required to accept this License, since you have not signed
+it. However, nothing else grants you permission to modify or distribute the
+Program or its derivative works. These actions are prohibited by law if you
+do not accept this License. Therefore, by modifying or distributing the Program
+(or any work based on the Program), you indicate your acceptance of this License
+to do so, and all its terms and conditions for copying, distributing or modifying
+the Program or works based on it.
+
+6. Each time you redistribute the Program (or any work based on the Program),
+the recipient automatically receives a license from the original licensor
+to copy, distribute or modify the Program subject to these terms and conditions.
+You may not impose any further restrictions on the recipients' exercise of
+the rights granted herein. You are not responsible for enforcing compliance
+by third parties to this License.
+
+7. If, as a consequence of a court judgment or allegation of patent infringement
+or for any other reason (not limited to patent issues), conditions are imposed
+on you (whether by court order, agreement or otherwise) that contradict the
+conditions of this License, they do not excuse you from the conditions of
+this License. If you cannot distribute so as to satisfy simultaneously your
+obligations under this License and any other pertinent obligations, then as
+a consequence you may not distribute the Program at all. For example, if a
+patent license would not permit royalty-free redistribution of the Program
+by all those who receive copies directly or indirectly through you, then the
+only way you could satisfy both it and this License would be to refrain entirely
+from distribution of the Program.
+
+If any portion of this section is held invalid or unenforceable under any
+particular circumstance, the balance of the section is intended to apply and
+the section as a whole is intended to apply in other circumstances.
+
+It is not the purpose of this section to induce you to infringe any patents
+or other property right claims or to contest validity of any such claims;
+this section has the sole purpose of protecting the integrity of the free
+software distribution system, which is implemented by public license practices.
+Many people have made generous contributions to the wide range of software
+distributed through that system in reliance on consistent application of that
+system; it is up to the author/donor to decide if he or she is willing to
+distribute software through any other system and a licensee cannot impose
+that choice.
+
+This section is intended to make thoroughly clear what is believed to be a
+consequence of the rest of this License.
+
+8. If the distribution and/or use of the Program is restricted in certain
+countries either by patents or by copyrighted interfaces, the original copyright
+holder who places the Program under this License may add an explicit geographical
+distribution limitation excluding those countries, so that distribution is
+permitted only in or among countries not thus excluded. In such case, this
+License incorporates the limitation as if written in the body of this License.
+
+9. The Free Software Foundation may publish revised and/or new versions of
+the General Public License from time to time. Such new versions will be similar
+in spirit to the present version, but may differ in detail to address new
+problems or concerns.
+
+Each version is given a distinguishing version number. If the Program specifies
+a version number of this License which applies to it and "any later version",
+you have the option of following the terms and conditions either of that version
+or of any later version published by the Free Software Foundation. If the
+Program does not specify a version number of this License, you may choose
+any version ever published by the Free Software Foundation.
+
+10. If you wish to incorporate parts of the Program into other free programs
+whose distribution conditions are different, write to the author to ask for
+permission. For software which is copyrighted by the Free Software Foundation,
+write to the Free Software Foundation; we sometimes make exceptions for this.
+Our decision will be guided by the two goals of preserving the free status
+of all derivatives of our free software and of promoting the sharing and reuse
+of software generally.
+
+   NO WARRANTY
+
+11. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR
+THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE
+STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM
+"AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING,
+BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE
+OF THE PROGRAM IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME
+THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
+
+12. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
+WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR REDISTRIBUTE
+THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY
+GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE
+OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF DATA
+OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES
+OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), EVEN IF SUCH
+HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
+END OF TERMS AND CONDITIONS
+
+How to Apply These Terms to Your New Programs
+
+If you develop a new program, and you want it to be of the greatest possible
+use to the public, the best way to achieve this is to make it free software
+which everyone can redistribute and change under these terms.
+
+To do so, attach the following notices to the program. It is safest to attach
+them to the start of each source file to most effectively convey the exclusion
+of warranty; and each file should have at least the "copyright" line and a
+pointer to where the full notice is found.
+
+<one line to give the program's name and an idea of what it does.>
+
+Copyright (C) <yyyy> <name of author>
+
+This program is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free Software
+Foundation; either version 2 of the License, or (at your option) any later
+version.
+
+This program is distributed in the hope that it will be useful, but WITHOUT
+ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License along with
+this program; if not, write to the Free Software Foundation, Inc., 51 Franklin
+Street, Fifth Floor, Boston, MA 02110-1301, USA.
+
+Also add information on how to contact you by electronic and paper mail.
+
+If the program is interactive, make it output a short notice like this when
+it starts in an interactive mode:
+
+Gnomovision version 69, Copyright (C) year name of author Gnomovision comes
+with ABSOLUTELY NO WARRANTY; for details type `show w'. This is free software,
+and you are welcome to redistribute it under certain conditions; type `show
+c' for details.
+
+The hypothetical commands `show w' and `show c' should show the appropriate
+parts of the General Public License. Of course, the commands you use may be
+called something other than `show w' and `show c'; they could even be mouse-clicks
+or menu items--whatever suits your program.
+
+You should also get your employer (if you work as a programmer) or your school,
+if any, to sign a "copyright disclaimer" for the program, if necessary. Here
+is a sample; alter the names:
+
+Yoyodyne, Inc., hereby disclaims all copyright interest in the program `Gnomovision'
+(which makes passes at compilers) written by James Hacker.
+
+<signature of Ty Coon>, 1 April 1989 Ty Coon, President of Vice This General
+Public License does not permit incorporating your program into proprietary
+programs. If your program is a subroutine library, you may consider it more
+useful to permit linking proprietary applications with the library. If this
+is what you want to do, use the GNU Lesser General Public License instead
+of this License.
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..b931c89
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,31 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+# SPDX-FileCopyrightText: 2020 Alyssa Ross <hi@alyssa.is>
+
+.POSIX:
+
+CFLAGS = -Wall -Wextra -O -g
+INSTALL = install
+INSTALL_PROGRAM = $(INSTALL)
+
+prefix = /usr/local
+bindir = $(prefix)/bin
+
+all: vsockclient vsockserver
+.PHONY: all
+
+install: vsockclient vsockserver
+	mkdir -p $(DESTDIR)$(bindir)
+	$(INSTALL_PROGRAM) vsockclient vsockserver $(DESTDIR)$(bindir)
+.PHONY: install
+
+vsockclient: vsockclient.o env.o log.o util.o vsock.o
+	$(CC) $(LDFLAGS) -o vsockclient vsockclient.c env.o log.o util.o vsock.o $(LDLIBS)
+vsockserver: vsockserver.o env.o log.o util.o vsock.o
+	$(CC) $(LDFLAGS) -o vsockserver vsockserver.c env.o log.o util.o vsock.o $(LDLIBS)
+
+vsockclient.o: env.h log.h util.h vsock.h
+vsockserver.o: env.h log.h util.h vsock.h
+
+clean:
+	rm -f env.o log.o util.o vsock.o vsockclient vsockserver
+.PHONY: clean
diff --git a/env.c b/env.c
new file mode 100644
index 0000000..4db8b2d
--- /dev/null
+++ b/env.c
@@ -0,0 +1,35 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+// SPDX-FileCopyrightText: 2020 Alyssa Ross <hi@alyssa.is>
+
+#define _GNU_SOURCE
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "env.h"
+
+int vsetenvf(const char *name, int overwrite, const char *fmt, va_list args)
+{
+	char *s;
+	int r;
+
+	if (vasprintf(&s, fmt, args) == -1)
+		return -1;
+
+	r = setenv(name, s, overwrite);
+
+	free(s);
+	return r;
+}
+
+int setenvf(const char *name, int overwrite, const char *fmt, ...)
+{
+	va_list ap;
+	int r;
+	
+	va_start(ap, fmt);
+	r = vsetenvf(name, overwrite, fmt, ap);
+	va_end(ap);
+
+	return r;
+}
diff --git a/env.h b/env.h
new file mode 100644
index 0000000..5429323
--- /dev/null
+++ b/env.h
@@ -0,0 +1,7 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+// SPDX-FileCopyrightText: 2020 Alyssa Ross <hi@alyssa.is>
+
+#include <stdarg.h>
+
+int setenvf(const char *name, int overwrite, const char *fmt, ...);
+int vsetenvf(const char *name, int overwrite, const char *fmt, va_list args);
diff --git a/log.c b/log.c
new file mode 100644
index 0000000..385d39f
--- /dev/null
+++ b/log.c
@@ -0,0 +1,55 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+// SPDX-FileCopyrightText: 2020 Alyssa Ross <hi@alyssa.is>
+
+#define _GNU_SOURCE
+
+#include "log.h"
+
+#include <err.h>
+#include <stdlib.h>
+
+enum verbosity verbosity = errors;
+
+void veloge(const char *fmt, va_list args)
+{
+	if (verbosity)
+		vwarn(fmt, args);
+}
+
+void velog(const char *fmt, va_list args)
+{
+	if (verbosity)
+		vwarnx(fmt, args);
+}
+
+void elog(const char *fmt, ...)
+{
+	va_list ap;
+	va_start(ap, fmt);
+	velog(fmt, ap);
+	va_end(ap);
+}
+
+void vilog(const char *fmt, va_list args)
+{
+	if (verbosity == all)
+		vwarnx(fmt, args);
+}
+
+void ilog(const char *fmt, ...)
+{
+	va_list ap;
+	va_start(ap, fmt);
+	vilog(fmt, ap);
+	va_end(ap);
+}
+
+void diee(int eval, const char *fmt, ...)
+{
+	va_list ap;
+	va_start(ap, fmt);
+	veloge(fmt, ap);
+	va_end(ap);
+
+	exit(eval);
+}
diff --git a/log.h b/log.h
new file mode 100644
index 0000000..a1b0c16
--- /dev/null
+++ b/log.h
@@ -0,0 +1,27 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+// SPDX-FileCopyrightText: 2020 Alyssa Ross <hi@alyssa.is>
+
+#include <stdarg.h>
+
+enum verbosity {
+	nothing,
+	errors,
+	all,
+};
+
+extern enum verbosity verbosity;
+
+// Log an error message, followed by strerrno(errno), then exit with
+// status eval.
+void diee(int eval, const char *fmt, ...) __attribute__((noreturn));
+
+// Log an error message.
+void elog(const char *fmt, ...);
+void velog(const char *fmt, va_list args);
+
+// Log an error message, followed by strerror(errno).
+void veloge(const char *fmt, va_list args);
+
+// Log an informative message.
+void ilog(const char *fmt, ...);
+void vilog(const char *fmt, va_list args);
diff --git a/util.c b/util.c
new file mode 100644
index 0000000..634dca4
--- /dev/null
+++ b/util.c
@@ -0,0 +1,37 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+// SPDX-FileCopyrightText: 2020 Alyssa Ross <hi@alyssa.is>
+
+#define _GNU_SOURCE
+
+#include "util.h"
+
+#include <ctype.h>
+#include <stdlib.h>
+
+int getu32(const char *s, uint32_t min, uint32_t max, uint32_t *out)
+{
+	unsigned long l;
+
+	if (getul(s, min, max, &l) == -1)
+		return -1;
+
+	*out = (uint32_t)l;
+
+	return 0;	
+}
+
+int getul(const char *s, unsigned long min, unsigned long max,
+	  unsigned long *out)
+{
+	char *endptr;
+
+	if (!s || !isdigit(s[0]) || (s[0] == '0' && s[1]))
+		return -1;
+
+	*out = strtoul(s, &endptr, 10);
+
+	if (*endptr || *out < min || *out > max)
+		return -1;
+
+	return 0;
+}
diff --git a/util.h b/util.h
new file mode 100644
index 0000000..64347d1
--- /dev/null
+++ b/util.h
@@ -0,0 +1,12 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+// SPDX-FileCopyrightText: 2020 Alyssa Ross <hi@alyssa.is>
+
+#include <stdint.h>
+
+// Strictly parse an integer from a string.  The integer must span the
+// whole string, not have any leading + or zeros, and be between min
+// and max (inclusive).
+
+int getu32(const char *s, uint32_t min, uint32_t max, uint32_t *out);
+int getul(const char *s, unsigned long min, unsigned long max,
+	  unsigned long *out);
diff --git a/vsock.c b/vsock.c
new file mode 100644
index 0000000..3bcd8b3
--- /dev/null
+++ b/vsock.c
@@ -0,0 +1,72 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+// SPDX-FileCopyrightText: 2020 Alyssa Ross <hi@alyssa.is>
+
+#define _GNU_SOURCE
+
+#include "vsock.h"
+
+#include <sys/ioctl.h>
+#include <sys/socket.h>
+
+#include <linux/vm_sockets.h>
+
+static void fill_sockaddr(struct sockaddr_vm *addr, uint32_t cid, uint32_t port)
+{
+	addr->svm_family = AF_VSOCK;
+	addr->svm_cid = cid;
+	addr->svm_port = port;
+}
+
+int vsock_bind(int fd, uint32_t cid, uint32_t port)
+{
+	struct sockaddr_vm addr = { 0 };
+	fill_sockaddr(&addr, cid, port);
+
+	if (bind(fd, (struct sockaddr *)&addr, sizeof addr) == -1)
+		return -1;
+
+	return 0;
+}
+
+int vsock_accept(int sockfd, uint32_t *cid, uint32_t *port)
+{
+	struct sockaddr_vm addr = { 0 };
+	socklen_t addr_size = sizeof addr;
+
+	if (accept(sockfd, (struct sockaddr *)&addr, &addr_size) == -1)
+		return -1;
+
+	*cid = addr.svm_cid;
+	*port = addr.svm_port;
+
+	return 0;
+}
+
+int vsock_connect(int fd, uint32_t cid, uint32_t port)
+{
+	struct sockaddr_vm addr = { 0 };
+	fill_sockaddr(&addr, cid, port);
+	return connect(fd, (struct sockaddr *)&addr, sizeof addr);
+}
+
+int vsock_open(uint32_t cid, uint32_t port)
+{
+	int fd = socket(AF_VSOCK, SOCK_STREAM, 0);
+	if (fd == -1)
+		return -1;
+
+	return vsock_connect(fd, cid, port);
+}
+
+int vsock_get_port(int fd, uint32_t *port)
+{
+	struct sockaddr_vm addr;
+	socklen_t addrlen = sizeof addr;
+
+	if (getsockname(fd, (struct sockaddr *)&addr, &addrlen) == -1)
+		return -1;
+
+	*port = addr.svm_port;
+
+	return 0;
+}
diff --git a/vsock.h b/vsock.h
new file mode 100644
index 0000000..e7d66c9
--- /dev/null
+++ b/vsock.h
@@ -0,0 +1,12 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+// SPDX-FileCopyrightText: 2020 Alyssa Ross <hi@alyssa.is>
+
+#include <stdint.h>
+
+int vsock_bind(int fd, uint32_t cid, uint32_t port);
+int vsock_accept(int sockfd, uint32_t *cid, uint32_t *port);
+
+int vsock_connect(int fd, uint32_t cid, uint32_t port);
+int vsock_open(uint32_t cid, uint32_t port);
+
+int vsock_get_port(int fd, uint32_t *port);
diff --git a/vsockclient.c b/vsockclient.c
new file mode 100644
index 0000000..ff8b7dc
--- /dev/null
+++ b/vsockclient.c
@@ -0,0 +1,88 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+// SPDX-FileCopyrightText: 2020 Alyssa Ross <hi@alyssa.is>
+
+#define _GNU_SOURCE
+
+#include <errno.h>
+#include <inttypes.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sysexits.h>
+#include <unistd.h>
+#include <sys/socket.h>
+
+#include <linux/vm_sockets.h>
+
+#include "env.h"
+#include "log.h"
+#include "util.h"
+#include "vsock.h"
+
+static void ex_usage(void) __attribute__((noreturn));
+static void ex_usage(void)
+{
+	if (verbosity)
+		fprintf(stderr, "Usage: %s [ -q | -Q | -v ] cid port prog...\n",
+			program_invocation_short_name);
+	exit(EX_USAGE);
+}
+
+int main(int argc, char *argv[])
+{
+	int opt, fd;
+	uint32_t rcid, rport;
+
+	while ((opt = getopt(argc, argv, "+qQv")) != -1) {
+		switch (opt) {
+		case 'q':
+			verbosity = nothing;
+			break;
+		case 'Q':
+			verbosity = errors;
+			break;
+		case 'v':
+			verbosity = all;
+			break;
+		default:
+			ex_usage();
+		}
+	}
+
+	// Check there are enough positional arguments (two for the
+	// address and at least one to exec into).
+	if (optind > argc - 3)
+		ex_usage();
+
+	if (getu32(argv[optind++], 0, UINT32_MAX, &rcid))
+		ex_usage();
+	if (getu32(argv[optind++], 0, UINT32_MAX, &rport))
+		ex_usage();
+
+	setenvf("VSOCKREMOTECID", 1, "%" PRIu32, rcid);
+	setenvf("VSOCKREMOTEPORT", 1, "%" PRIu32, rport);
+
+	ilog("connecting to %" PRIu32 ":%" PRIu32 "...", rcid, rport);
+
+	// Linux will sometimes randomly time out connections, even on
+	// the same host with no backlog, so retry a few times.
+	{
+		int i = 0;
+		do fd = vsock_open(rcid, rport);
+		while (i++ < 3 && fd == -1 && errno == ETIMEDOUT);
+	}
+	if (fd == -1)
+		diee(EX_UNAVAILABLE,
+		     "connect to %" PRIu32 ":%" PRIu32 " failed", rcid, rport);
+	ilog("connected to %" PRIu32 ":%" PRIu32 "!", rcid, rport);
+
+	// Set up the file descriptors to the well-known UCSPI numbers.
+	if (dup2(fd, 6) == -1)
+		diee(EX_OSERR, "dup2");
+	if (dup2(fd, 7) == -1)
+		diee(EX_OSERR, "dup2");
+	if (fd != 6 && fd != 7)
+		close(fd);
+
+	execvp(argv[optind], &argv[optind]);
+	diee(EX_OSERR, "exec");
+}
diff --git a/vsockserver.c b/vsockserver.c
new file mode 100644
index 0000000..dd9a74a
--- /dev/null
+++ b/vsockserver.c
@@ -0,0 +1,126 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+// SPDX-FileCopyrightText: 2020 Alyssa Ross <hi@alyssa.is>
+
+#define _GNU_SOURCE
+
+#include <err.h>
+#include <errno.h>
+#include <inttypes.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <sys/wait.h>
+#include <sysexits.h>
+#include <unistd.h>
+
+#include <linux/vm_sockets.h>
+
+#include "env.h"
+#include "log.h"
+#include "util.h"
+#include "vsock.h"
+
+static void ex_usage(void) __attribute__((noreturn));
+static void ex_usage(void)
+{
+	if (verbosity)
+		fprintf(stderr, "Usage: %s [ -1 ] [ -q | -Q | -v ] cid port prog...\n",
+			program_invocation_short_name);
+	exit(EX_USAGE);
+}
+
+int main(int argc, char *argv[])
+{
+	bool notify = false;
+	int opt, conn;
+	pid_t child;
+	uint32_t lcid, lport, rcid, rport;
+
+	while ((opt = getopt(argc, argv, "+1qQv")) != -1) {
+		switch (opt) {
+		case '1':
+			notify = true;
+			break;
+		case 'q':
+			verbosity = nothing;
+			break;
+		case 'Q':
+			verbosity = errors;
+			break;
+		case 'v':
+			verbosity = all;
+			break;
+		default:
+			ex_usage();
+		}
+	}
+
+	// Check there are enough positional arguments (two for the
+	// address and at least one to exec into).
+	if (optind > argc - 3)
+		ex_usage();
+	
+	if (!strcmp(argv[optind], "-1"))
+		lcid = VMADDR_CID_ANY;
+	else if (getu32(argv[optind], 0, UINT32_MAX, &lcid))
+		ex_usage();
+	optind++;
+
+	if (!strcmp(argv[optind], "-1"))
+		lport = VMADDR_PORT_ANY;
+	else if (getu32(argv[optind], 0, UINT32_MAX, &lport))
+		ex_usage();
+	optind++;
+
+	int fd = socket(AF_VSOCK, SOCK_STREAM, 0);
+	if (fd == -1)
+		diee(EX_OSERR, "socket");
+
+	if (vsock_bind(fd, lcid, lport) == -1)
+		diee(EX_OSERR, "bind");
+
+	if (listen(fd, 40) == -1)
+		diee(EX_OSERR, "listen");
+
+	if (lport == VMADDR_PORT_ANY)
+		if (vsock_get_port(fd, &lport) == -1)
+			diee(EX_OSERR, "getsockname");
+
+	if (notify) {
+		printf("%" PRIu32 "\n", lport);
+		close(STDOUT_FILENO);
+	}
+
+	setenvf("VSOCKLOCALCID", 1, "%" PRIu32, lcid);
+	setenvf("VSOCKLOCALPORT", 1, "%" PRIu32, lport);
+
+	ilog("listening as %" PRIu32 " on port %" PRIu32, lcid, lport);
+
+	while ((conn = vsock_accept(fd, &rcid, &rport)) != -1) {
+		setenvf("VSOCKREMOTECID", 1, "%" PRIu32, rcid);
+		setenvf("VSOCKREMOTEPORT", 1, "%" PRIu32, rport);
+
+		ilog("connection from %" PRIu32 " port %" PRIu32, rcid, rport);
+
+		switch (child = fork()) {
+		case -1: err(EX_OSERR, "fork");
+		case 0:
+			if (dup2(conn, STDIN_FILENO) == -1)
+				err(EX_OSERR, "dup2");
+			if (dup2(conn, STDOUT_FILENO) == -1)
+				err(EX_OSERR, "dup2");
+			if (conn != 0 && conn != 1)
+				close(conn);
+			execvp(argv[optind], &argv[optind]);
+			err(EX_OSERR, "exec");
+		}
+
+		if (waitpid(child, NULL, 0) == -1)
+			err(EX_OSERR, "waitpid");
+		
+		close(conn);
+	}
+	err(EX_OSERR, "accept");
+}