[PATCH v4 10/17] pesto, conf: Have pesto connect to passt and check versions

David Gibson
2026-04-21T04:42:28Z

Start implementing pesto in earnest. Create a control/configuration
socket in passt. Have pesto connect to it and retrieve a server greeting
Perform some basic version checking.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
Makefile | 8 ++-
conf.c | 160 ++++++++++++++++++++++++++++++++++++++++++++++++++-
conf.h | 2 +
epoll_type.h | 4 ++
passt.1 | 5 ++
passt.c | 8 +++
passt.h | 6 ++
pesto.c | 47 ++++++++++++++-
pesto.h | 22 +++++++
serialise.c | 3 +
10 files changed, 259 insertions(+), 6 deletions(-)

diff --git a/Makefile b/Makefile
index f6cec8a8..1718ddbf 100644
--- a/Makefile
+++ b/Makefile
@@ -47,7 +47,7 @@ PASST_SRCS = arch.c arp.c bitmap.c checksum.c conf.c dhcp.c dhcpv6.c \
vhost_user.c virtio.c vu_common.c
QRAP_SRCS = qrap.c
PASST_REPAIR_SRCS = passt-repair.c
-PESTO_SRCS = pesto.c
+PESTO_SRCS = pesto.c serialise.c
SRCS = $(PASST_SRCS) $(QRAP_SRCS) $(PASST_REPAIR_SRCS) $(PESTO_SRCS)

MANPAGES = passt.1 pasta.1 pesto.1 qrap.1 passt-repair.1
@@ -61,7 +61,7 @@ PASST_HEADERS = arch.h arp.h bitmap.h checksum.h common.h conf.h dhcp.h \
vhost_user.h virtio.h vu_common.h
QRAP_HEADERS = arp.h ip.h passt.h util.h
PASST_REPAIR_HEADERS = linux_dep.h
-PESTO_HEADERS = common.h pesto.h log.h
+PESTO_HEADERS = common.h pesto.h log.h serialise.h

C := \#include <sys/random.h>\nint main(){int a=getrandom(0, 0, 0);}
ifeq ($(shell printf "$(C)" | $(CC) -S -xc - -o - >/dev/null 2>&1; echo $$?),0)
@@ -228,7 +228,9 @@ passt.cppcheck: $(PASST_SRCS) $(PASST_HEADERS) seccomp.h
passt-repair.cppcheck: $(PASST_REPAIR_SRCS) $(PASST_REPAIR_HEADERS) seccomp_repair.h

pesto.cppcheck: BASE_CPPFLAGS += -DPESTO
-pesto.cppcheck: CPPCHECK_FLAGS += --suppress=unmatchedSuppression
+pesto.cppcheck: CPPCHECK_FLAGS += \
+ --suppress=unusedFunction:serialise.c \
+ --suppress=staticFunction:serialise.c
pesto.cppcheck: $(PESTO_SRCS) $(PESTO_HEADERS) seccomp_pesto.h

qrap.cppcheck: BASE_CPPFLAGS += -DARCH=\"$(TARGET_ARCH)\"
diff --git a/conf.c b/conf.c
index 05861072..75d816ac 100644
--- a/conf.c
+++ b/conf.c
@@ -48,6 +48,10 @@
#include "isolation.h"
#include "log.h"
#include "vhost_user.h"
+#include "epoll_ctl.h"
+#include "conf.h"
+#include "pesto.h"
+#include "serialise.h"

#define NETNS_RUN_DIR "/run/netns"

@@ -541,6 +545,7 @@ static void usage(const char *name, FILE *f, int status)
" --runas UID|UID:GID Run as given UID, GID, which can be\n"
" numeric, or login and group names\n"
" default: drop to user \"nobody\"\n"
+ " -c, --conf-path PATH Configuration socket path\n"
" -h, --help Display this help message and exit\n"
" --version Show version and exit\n");

@@ -779,6 +784,9 @@ static void conf_print(const struct ctx *c)
char buf[INANY_ADDRSTRLEN];
int i;

+ if (c->fd_control_listen >= 0)
+ info("Configuration socket: %s", c->control_path);
+
if (c->ifi4 > 0 || c->ifi6 > 0) {
char ifn[IFNAMSIZ];

@@ -1072,6 +1080,17 @@ static void conf_open_files(struct ctx *c)
if (c->pidfile_fd < 0)
die_perror("Couldn't open PID file %s", c->pidfile);
}
+
+ c->fd_control = -1;
+ if (*c->control_path) {
+ c->fd_control_listen = sock_unix(c->control_path);
+ if (c->fd_control_listen < 0) {
+ die_perror("Couldn't open control socket %s",
+ c->control_path);
+ }
+ } else {
+ c->fd_control_listen = -1;
+ }
}

/**
@@ -1107,6 +1126,25 @@ fail:
die("Invalid MAC address: %s", str);
}

+/**
+ * conf_sock_listen() - Start listening for connections on configuration socket
+ * @c: Execution context
+ */
+static void conf_sock_listen(const struct ctx *c)
+{
+ union epoll_ref ref = { .type = EPOLL_TYPE_CONF_LISTEN };
+
+ if (c->fd_control_listen < 0)
+ return;
+
+ if (listen(c->fd_control_listen, 0))
+ die_perror("Couldn't listen on configuration socket");
+
+ ref.fd = c->fd_control_listen;
+ if (epoll_add(c->epollfd, EPOLLIN | EPOLLET, ref))
+ die_perror("Couldn't add configuration socket to epoll");
+}
+
/**
* conf() - Process command-line arguments and set configuration
* @c: Execution context
@@ -1189,9 +1227,10 @@ void conf(struct ctx *c, int argc, char **argv)
{"migrate-exit", no_argument, NULL, 29 },
{"migrate-no-linger", no_argument, NULL, 30 },
{"stats", required_argument, NULL, 31 },
+ {"conf-path", required_argument, NULL, 'c' },
{ 0 },
};
- const char *optstring = "+dqfel:hs:F:I:p:P:m:a:n:M:g:i:o:D:S:H:461t:u:T:U:";
+ const char *optstring = "+dqfel:hs:c:F:I:p:P:m:a:n:M:g:i:o:D:S:H:461t:u:T:U:";
const char *logname = (c->mode == MODE_PASTA) ? "pasta" : "passt";
bool opt_t = false, opt_T = false, opt_u = false, opt_U = false;
char userns[PATH_MAX] = { 0 }, netns[PATH_MAX] = { 0 };
@@ -1449,6 +1488,13 @@ void conf(struct ctx *c, int argc, char **argv)

c->fd_tap = -1;
break;
+ case 'c':
+ ret = snprintf(c->control_path, sizeof(c->control_path),
+ "%s", optarg);
+ if (ret <= 0 || ret >= (int)sizeof(c->sock_path))
+ die("Invalid configuration path: %s", optarg);
+ c->fd_control_listen = c->fd_control = -1;
+ break;
case 'F':
errno = 0;
fd_tap_opt = strtol(optarg, NULL, 0);
@@ -1871,6 +1917,118 @@ void conf(struct ctx *c, int argc, char **argv)
fwd_rule_parse('U', "auto", c->fwd[PIF_SPLICE]);
}

+ conf_sock_listen(c);
+
if (!c->quiet)
conf_print(c);
}
+
+/**
+ * conf_close() - Close configuration / control socket and clean up
+ * @c: Execution context
+ */
+static void conf_close(struct ctx *c)
+{
+ debug("Closing configuration socket");
+ epoll_ctl(c->epollfd, EPOLL_CTL_DEL, c->fd_control, NULL);
+ close(c->fd_control);
+ c->fd_control = -1;
+}
+
+/**
+ * conf_listen_handler() - Handle events on configuration listening socket
+ * @c: Execution context
+ * @events: epoll events
+ */
+void conf_listen_handler(struct ctx *c, uint32_t events)
+{
+ struct pesto_hello hello = {
+ .magic = PESTO_SERVER_MAGIC,
+ .version = htonl(PESTO_PROTOCOL_VERSION),
+ };
+ union epoll_ref ref = { .type = EPOLL_TYPE_CONF };
+ struct ucred uc = { 0 };
+ socklen_t len = sizeof(uc);
+ int fd, rc;
+
+ if (events != EPOLLIN) {
+ err("Unexpected event 0x%04x on configuration socket", events);
+ return;
+ }
+
+ fd = accept4(c->fd_control_listen, NULL, NULL, SOCK_NONBLOCK);
+ if (fd < 0) {
+ warn_perror("accept4() on configuration listening socket");
+ return;
+ }
+
+ if (getsockopt(fd, SOL_SOCKET, SO_PEERCRED, &uc, &len) < 0)
+ warn_perror("Can't get configuration client credentials");
+
+ /* Another client is already connected: accept and close right away. */
+ if (c->fd_control != -1) {
+ info("Discarding configuration client, PID %i", uc.pid);
+ goto fail;
+ }
+
+ c->fd_control = ref.fd = fd;
+ rc = epoll_add(c->epollfd, EPOLLIN | EPOLLET, ref);
+ if (rc < 0) {
+ warn_perror("epoll_ctl() on configuration socket");
+ goto fail;
+ }
+
+ rc = write_all_buf(fd, &hello, sizeof(hello));
+ if (rc < 0) {
+ warn_perror("Error writing configuration protocol hello");
+ goto fail;
+ }
+
+ info("Accepted configuration client, PID %i", uc.pid);
+ if (!PESTO_PROTOCOL_VERSION) {
+ warn(
+"Warning: Using experimental unsupported configuration protocol");
+ }
+
+ return;
+
+fail:
+ conf_close(c);
+}
+
+/**
+ * conf_handler() - Handle events on configuration socket
+ * @c: Execution context
+ * @events: epoll events
+ */
+void conf_handler(struct ctx *c, uint32_t events)
+{
+ if (events & EPOLLIN) {
+ char discard[BUFSIZ];
+ ssize_t n;
+
+ do {
+ n = read(c->fd_control, discard, sizeof(discard));
+ if (n > 0)
+ debug("Discarded %zd bytes of config data", n);
+ } while (n > 0);
+ if (n == 0) {
+ debug("Configuration client EOF");
+ goto close;
+ }
+ if (errno != EAGAIN && errno != EWOULDBLOCK) {
+ err_perror("Error reading config data");
+ goto close;
+ }
+ }
+
+ if (events & EPOLLHUP) {
+ debug("Configuration client hangup");
+ goto close;
+ }
+
+ return;
+
+close:
+ conf_close(c);
+}
diff --git a/conf.h b/conf.h
index b45ad746..16f97189 100644
--- a/conf.h
+++ b/conf.h
@@ -8,5 +8,7 @@

enum passt_modes conf_mode(int argc, char *argv[]);
void conf(struct ctx *c, int argc, char **argv);
+void conf_listen_handler(struct ctx *c, uint32_t events);
+void conf_handler(struct ctx *c, uint32_t events);

#endif /* CONF_H */
diff --git a/epoll_type.h b/epoll_type.h
index a90ffb67..061325aa 100644
--- a/epoll_type.h
+++ b/epoll_type.h
@@ -46,6 +46,10 @@ enum epoll_type {
EPOLL_TYPE_REPAIR,
/* Netlink neighbour subscription socket */
EPOLL_TYPE_NL_NEIGH,
+ /* Configuration listening socket */
+ EPOLL_TYPE_CONF_LISTEN,
+ /* Configuration socket */
+ EPOLL_TYPE_CONF,

EPOLL_NUM_TYPES,
};
diff --git a/passt.1 b/passt.1
index 6303aeb0..908fd4a4 100644
--- a/passt.1
+++ b/passt.1
@@ -127,6 +127,11 @@ login name and group name can be passed. This requires privileges (either
initial effective UID 0 or CAP_SETUID capability) to work.
Default is to change to user \fInobody\fR if started as root.

+.TP
+.BR \-c ", " \-\-conf-path " " \fIpath " " (EXPERIMENTAL)
+Path for configuration and control socket used by \fBpesto\fR(1) to
+dynamically update passt or pasta's configuration.
+
.TP
.BR \-h ", " \-\-help
Display a help message and exit.
diff --git a/passt.c b/passt.c
index f84419c7..bc42ea33 100644
--- a/passt.c
+++ b/passt.c
@@ -80,6 +80,8 @@ char *epoll_type_str[] = {
[EPOLL_TYPE_REPAIR_LISTEN] = "TCP_REPAIR helper listening socket",
[EPOLL_TYPE_REPAIR] = "TCP_REPAIR helper socket",
[EPOLL_TYPE_NL_NEIGH] = "netlink neighbour notifier socket",
+ [EPOLL_TYPE_CONF_LISTEN] = "configuration listening socket",
+ [EPOLL_TYPE_CONF] = "configuration socket",
};
static_assert(ARRAY_SIZE(epoll_type_str) == EPOLL_NUM_TYPES,
"epoll_type_str[] doesn't match enum epoll_type");
@@ -303,6 +305,12 @@ static void passt_worker(void *opaque, int nfds, struct epoll_event *events)
case EPOLL_TYPE_NL_NEIGH:
nl_neigh_notify_handler(c);
break;
+ case EPOLL_TYPE_CONF_LISTEN:
+ conf_listen_handler(c, eventmask);
+ break;
+ case EPOLL_TYPE_CONF:
+ conf_handler(c, eventmask);
+ break;
default:
/* Can't happen */
assert(0);
diff --git a/passt.h b/passt.h
index 62b8dcdf..b3f049de 100644
--- a/passt.h
+++ b/passt.h
@@ -158,6 +158,7 @@ struct ip6_ctx {
* @foreground: Run in foreground, don't log to stderr by default
* @nofile: Maximum number of open files (ulimit -n)
* @sock_path: Path for UNIX domain socket
+ * @control_path: Path for control/configuration UNIX domain socket
* @repair_path: TCP_REPAIR helper path, can be "none", empty for default
* @pcap: Path for packet capture file
* @pidfile: Path to PID file, empty string if not configured
@@ -169,6 +170,8 @@ struct ip6_ctx {
* @epollfd: File descriptor for epoll instance
* @fd_tap_listen: File descriptor for listening AF_UNIX socket, if any
* @fd_tap: AF_UNIX socket, tuntap device, or pre-opened socket
+ * @fd_control_listen: Listening control/configuration socket, if any
+ * @fd_control: Control/configuration socket, if any
* @fd_repair_listen: File descriptor for listening TCP_REPAIR socket, if any
* @fd_repair: Connected AF_UNIX socket for TCP_REPAIR helper
* @our_tap_mac: Pasta/passt's MAC on the tap link
@@ -223,6 +226,7 @@ struct ctx {
int foreground;
int nofile;
char sock_path[UNIX_PATH_MAX];
+ char control_path[UNIX_PATH_MAX];
char repair_path[UNIX_PATH_MAX];
char pcap[PATH_MAX];

@@ -240,6 +244,8 @@ struct ctx {
int epollfd;
int fd_tap_listen;
int fd_tap;
+ int fd_control_listen;
+ int fd_control;
int fd_repair_listen;
int fd_repair;
unsigned char our_tap_mac[ETH_ALEN];
diff --git a/pesto.c b/pesto.c
index f0916e82..5e191283 100644
--- a/pesto.c
+++ b/pesto.c
@@ -33,6 +33,7 @@

#include "common.h"
#include "seccomp_pesto.h"
+#include "serialise.h"
#include "pesto.h"
#include "log.h"

@@ -66,6 +67,8 @@ static void usage(const char *name, FILE *f, int status)
*
* Return: 0 on success, won't return on failure
*
+ * #syscalls:pesto socket s390x:socketcall i686:socketcall
+ * #syscalls:pesto connect shutdown close
* #syscalls:pesto exit_group fstat read write
*/
int main(int argc, char **argv)
@@ -76,9 +79,12 @@ int main(int argc, char **argv)
{"version", no_argument, NULL, 1 },
{ 0 },
};
+ struct sockaddr_un a = { AF_UNIX, "" };
const char *optstring = "dh";
+ struct pesto_hello hello;
struct sock_fprog prog;
- int optname;
+ int optname, ret, s;
+ uint32_t s_version;

prctl(PR_SET_DUMPABLE, 0);

@@ -122,5 +128,42 @@ int main(int argc, char **argv)

debug("debug_flag=%d, path=\"%s\"", debug_flag, argv[optind]);

- die("pesto is not implemented yet");
+ if ((s = socket(AF_UNIX, SOCK_STREAM, 0)) < 0)
+ die_perror("Failed to create AF_UNIX socket");
+
+ ret = snprintf(a.sun_path, sizeof(a.sun_path), "%s", argv[optind]);
+ if (ret <= 0 || ret >= (int)sizeof(a.sun_path))
+ die("Invalid socket path \"%s\"", argv[1]);
+
+ ret = connect(s, (struct sockaddr *)&a, sizeof(a));
+ if (ret < 0) {
+ die_perror("Failed to connect to %s", a.sun_path);
+ }
+
+ ret = read_all_buf(s, &hello, sizeof(hello));
+ if (ret < 0)
+ die_perror("Couldn't read server greeting");
+
+ if (memcmp(hello.magic, PESTO_SERVER_MAGIC, sizeof(hello.magic)))
+ die("Bad magic number from server");
+
+ s_version = ntohl(hello.version);
+
+ if (s_version > PESTO_PROTOCOL_VERSION) {
+ die("Unknown server protocol version %"PRIu32" > %"PRIu32"\n",
+ s_version, PESTO_PROTOCOL_VERSION);
+ }
+
+ /* cppcheck-suppress knownConditionTrueFalse */
+ if (!s_version) {
+ if (PESTO_PROTOCOL_VERSION)
+ die("Unsupported experimental server protocol");
+ FPRINTF(stderr,
+"Warning: Using experimental protocol version, client and server must match\n");
+ }
+
+ if (shutdown(s, SHUT_RDWR) < 0 || close(s) < 0)
+ die_perror("Error shutting down control socket");
+
+ exit(0);
}
diff --git a/pesto.h b/pesto.h
index e9b329f4..92d4df3a 100644
--- a/pesto.h
+++ b/pesto.h
@@ -9,4 +9,26 @@
#ifndef PESTO_H
#define PESTO_H

+#include <assert.h>
+#include <stdint.h>
+
+#define PESTO_SERVER_MAGIC "pesto:s"
+
+/* Version 0 is reserved for unreleased / unsupported experimental versions */
+#define PESTO_PROTOCOL_VERSION 0
+
+/**
+ * struct pesto_hello - Server introduction message
+ * @magic: PESTO_SERVER_MAGIC
+ * @version: Version number
+ */
+struct pesto_hello {
+ char magic[8];
+ uint32_t version;
+} __attribute__ ((__packed__));
+
+static_assert(sizeof(PESTO_SERVER_MAGIC)
+ == sizeof(((struct pesto_hello *)0)->magic),
+ "PESTO_SERVER_MAGIC has wrong size");
+
#endif /* PESTO_H */
diff --git a/serialise.c b/serialise.c
index 944e7414..346df998 100644
--- a/serialise.c
+++ b/serialise.c
@@ -6,6 +6,9 @@
* PASTA - Pack A Subtle Tap Abstraction
* for network namespace/tap device mode
*
+ * PESTO - Programmable Extensible Socket Translation Orchestrator
+ * front-end for passt(1) and pasta(1) forwarding configuration
+ *
* serialise.c - Serialisation of data structures over bytestreams
*
* Copyright Red Hat
--
2.53.0