1 files changed, 255 insertions, 0 deletions
diff --git a/repair.c b/repair.c
new file mode 100644
index 0000000..149fe51
--- /dev/null
+++ b/repair.c
@@ -0,0 +1,255 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+/* PASST - Plug A Simple Socket Transport
+ *  for qemu/UNIX domain socket mode
+ *
+ * PASTA - Pack A Subtle Tap Abstraction
+ *  for network namespace/tap device mode
+ *
+ * repair.c - Interface (server) for passt-repair, set/clear TCP_REPAIR
+ *
+ * Copyright (c) 2025 Red Hat GmbH
+ * Author: Stefano Brivio <sbrivio@redhat.com>
+ */
+
+#include <errno.h>
+#include <sys/socket.h>
+#include <sys/uio.h>
+
+#include "util.h"
+#include "ip.h"
+#include "passt.h"
+#include "inany.h"
+#include "flow.h"
+#include "flow_table.h"
+
+#include "repair.h"
+
+#define SCM_MAX_FD 253 /* From Linux kernel (include/net/scm.h), not in UAPI */
+
+/* Wait for a while for TCP_REPAIR helper to connect if it's not there yet */
+#define REPAIR_ACCEPT_TIMEOUT_MS	10
+#define REPAIR_ACCEPT_TIMEOUT_US	(REPAIR_ACCEPT_TIMEOUT_MS * 1000)
+
+/* Pending file descriptors for next repair_flush() call, or command change */
+static int repair_fds[SCM_MAX_FD];
+
+/* Pending command: flush pending file descriptors if it changes */
+static int8_t repair_cmd;
+
+/* Number of pending file descriptors set in @repair_fds */
+static int repair_nfds;
+
+/**
+ * repair_sock_init() - Start listening for connections on helper socket
+ * @c:		Execution context
+ */
+void repair_sock_init(const struct ctx *c)
+{
+	union epoll_ref ref = { .type = EPOLL_TYPE_REPAIR_LISTEN };
+	struct epoll_event ev = { 0 };
+
+	if (c->fd_repair_listen == -1)
+		return;
+
+	if (listen(c->fd_repair_listen, 0)) {
+		err_perror("listen() on repair helper socket, won't migrate");
+		return;
+	}
+
+	ref.fd = c->fd_repair_listen;
+	ev.events = EPOLLIN | EPOLLHUP | EPOLLET;
+	ev.data.u64 = ref.u64;
+	if (epoll_ctl(c->epollfd, EPOLL_CTL_ADD, c->fd_repair_listen, &ev))
+		err_perror("repair helper socket epoll_ctl(), won't migrate");
+}
+
+/**
+ * repair_listen_handler() - Handle events on TCP_REPAIR helper listening socket
+ * @c:		Execution context
+ * @events:	epoll events
+ */
+void repair_listen_handler(struct ctx *c, uint32_t events)
+{
+	union epoll_ref ref = { .type = EPOLL_TYPE_REPAIR };
+	struct epoll_event ev = { 0 };
+	struct ucred ucred;
+	socklen_t len;
+
+	if (events != EPOLLIN) {
+		debug("Spurious event 0x%04x on TCP_REPAIR helper socket",
+		      events);
+		return;
+	}
+
+	len = sizeof(ucred);
+
+	/* Another client is already connected: accept and close right away. */
+	if (c->fd_repair != -1) {
+		int discard = accept4(c->fd_repair_listen, NULL, NULL,
+				      SOCK_NONBLOCK);
+
+		if (discard == -1)
+			return;
+
+		if (!getsockopt(discard, SOL_SOCKET, SO_PEERCRED, &ucred, &len))
+			info("Discarding TCP_REPAIR helper, PID %i", ucred.pid);
+
+		close(discard);
+		return;
+	}
+
+	if ((c->fd_repair = accept4(c->fd_repair_listen, NULL, NULL, 0)) < 0) {
+		debug_perror("accept4() on TCP_REPAIR helper listening socket");
+		return;
+	}
+
+	if (!getsockopt(c->fd_repair, SOL_SOCKET, SO_PEERCRED, &ucred, &len))
+		info("Accepted TCP_REPAIR helper, PID %i", ucred.pid);
+
+	ref.fd = c->fd_repair;
+	ev.events = EPOLLHUP | EPOLLET;
+	ev.data.u64 = ref.u64;
+	if (epoll_ctl(c->epollfd, EPOLL_CTL_ADD, c->fd_repair, &ev)) {
+		debug_perror("epoll_ctl() on TCP_REPAIR helper socket");
+		close(c->fd_repair);
+		c->fd_repair = -1;
+	}
+}
+
+/**
+ * repair_close() - Close connection to TCP_REPAIR helper
+ * @c:		Execution context
+ */
+void repair_close(struct ctx *c)
+{
+	debug("Closing TCP_REPAIR helper socket");
+
+	epoll_ctl(c->epollfd, EPOLL_CTL_DEL, c->fd_repair, NULL);
+	close(c->fd_repair);
+	c->fd_repair = -1;
+}
+
+/**
+ * repair_handler() - Handle EPOLLHUP and EPOLLERR on TCP_REPAIR helper socket
+ * @c:		Execution context
+ * @events:	epoll events
+ */
+void repair_handler(struct ctx *c, uint32_t events)
+{
+	(void)events;
+
+	repair_close(c);
+}
+
+/**
+ * repair_wait() - Wait (with timeout) for TCP_REPAIR helper to connect
+ * @c:		Execution context
+ */
+void repair_wait(struct ctx *c)
+{
+	struct timeval tv = { .tv_sec = 0,
+			      .tv_usec = (long)(REPAIR_ACCEPT_TIMEOUT_US) };
+	static_assert(REPAIR_ACCEPT_TIMEOUT_US < 1000 * 1000,
+		      ".tv_usec is greater than 1000 * 1000");
+
+	if (c->fd_repair >= 0 || c->fd_repair_listen == -1)
+		return;
+
+	if (setsockopt(c->fd_repair_listen, SOL_SOCKET, SO_RCVTIMEO,
+		       &tv, sizeof(tv))) {
+		err_perror("Set timeout on TCP_REPAIR listening socket");
+		return;
+	}
+
+	repair_listen_handler(c, EPOLLIN);
+
+	tv.tv_usec = 0;
+	if (setsockopt(c->fd_repair_listen, SOL_SOCKET, SO_RCVTIMEO,
+		       &tv, sizeof(tv)))
+		err_perror("Clear timeout on TCP_REPAIR listening socket");
+}
+
+/**
+ * repair_flush() - Flush current set of sockets to helper, with current command
+ * @c:		Execution context
+ *
+ * Return: 0 on success, negative error code on failure
+ */
+int repair_flush(struct ctx *c)
+{
+	char buf[CMSG_SPACE(sizeof(int) * SCM_MAX_FD)]
+	     __attribute__ ((aligned(__alignof__(struct cmsghdr)))) = { 0 };
+	struct iovec iov = { &repair_cmd, sizeof(repair_cmd) };
+	struct cmsghdr *cmsg;
+	struct msghdr msg;
+	int8_t reply;
+
+	if (!repair_nfds)
+		return 0;
+
+	msg = (struct msghdr){ .msg_name = NULL, .msg_namelen = 0,
+			       .msg_iov = &iov, .msg_iovlen = 1,
+			       .msg_control = buf,
+			       .msg_controllen = CMSG_SPACE(sizeof(int) *
+							    repair_nfds),
+			       .msg_flags = 0 };
+	cmsg = CMSG_FIRSTHDR(&msg);
+
+	cmsg->cmsg_level = SOL_SOCKET;
+	cmsg->cmsg_type = SCM_RIGHTS;
+	cmsg->cmsg_len = CMSG_LEN(sizeof(int) * repair_nfds);
+	memcpy(CMSG_DATA(cmsg), repair_fds, sizeof(int) * repair_nfds);
+
+	repair_nfds = 0;
+
+	if (sendmsg(c->fd_repair, &msg, 0) < 0) {
+		int ret = -errno;
+		err_perror("Failed to send sockets to TCP_REPAIR helper");
+		repair_close(c);
+		return ret;
+	}
+
+	if (recv(c->fd_repair, &reply, sizeof(reply), 0) < 0) {
+		int ret = -errno;
+		err_perror("Failed to receive reply from TCP_REPAIR helper");
+		repair_close(c);
+		return ret;
+	}
+
+	if (reply != repair_cmd) {
+		err("Unexpected reply from TCP_REPAIR helper: %d", reply);
+		repair_close(c);
+		return -ENXIO;
+	}
+
+	return 0;
+}
+
+/**
+ * repair_set() - Add socket to TCP_REPAIR set with given command
+ * @c:		Execution context
+ * @s:		Socket to add
+ * @cmd:	TCP_REPAIR_ON, TCP_REPAIR_OFF, or TCP_REPAIR_OFF_NO_WP
+ *
+ * Return: 0 on success, negative error code on failure
+ */
+int repair_set(struct ctx *c, int s, int cmd)
+{
+	int rc;
+
+	if (repair_nfds && repair_cmd != cmd) {
+		if ((rc = repair_flush(c)))
+			return rc;
+	}
+
+	repair_cmd = cmd;
+	repair_fds[repair_nfds++] = s;
+
+	if (repair_nfds >= SCM_MAX_FD) {
+		if ((rc = repair_flush(c)))
+			return rc;
+	}
+
+	return 0;
+}