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| | // SPDX-License-Identifier: GPL-2.0-or-later
/* PASST - Plug A Simple Socket Transport
* for qemu/UNIX domain socket mode
*
* passt-repair.c - Privileged helper to set/clear TCP_REPAIR on sockets
*
* Copyright (c) 2025 Red Hat GmbH
* Author: Stefano Brivio <sbrivio@redhat.com>
*
* Connect to passt via UNIX domain socket, receive sockets via SCM_RIGHTS along
* with commands mapping to TCP_REPAIR values, and switch repair mode on or
* off. Reply by echoing the command. Exit if the command is INT_MAX.
*/
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <limits.h>
#include <unistd.h>
#include <netdb.h>
#include <netinet/tcp.h>
#define SCM_MAX_FD 253 /* From Linux kernel (include/net/scm.h), not in UAPI */
int main(int argc, char **argv)
{
char buf[CMSG_SPACE(sizeof(int) * SCM_MAX_FD)]
__attribute__ ((aligned(__alignof__(struct cmsghdr))));
struct sockaddr_un a = { AF_UNIX, "" };
int cmd, fds[SCM_MAX_FD], s, ret, i;
struct cmsghdr *cmsg;
struct msghdr msg;
struct iovec iov;
iov = (struct iovec){ &cmd, sizeof(cmd) };
msg = (struct msghdr){ NULL, 0, &iov, 1, buf, sizeof(buf), 0 };
cmsg = CMSG_FIRSTHDR(&msg);
if (argc != 2) {
fprintf(stderr, "Usage: %s PATH\n", argv[0]);
return -1;
}
ret = snprintf(a.sun_path, sizeof(a.sun_path), "%s", argv[1]);
if (ret <= 0 || ret >= (int)sizeof(a.sun_path)) {
fprintf(stderr, "Invalid socket path: %s\n", argv[1]);
return -1;
}
if ((s = socket(AF_UNIX, SOCK_STREAM, 0)) < 0) {
perror("Failed to create AF_UNIX socket");
return -1;
}
if (connect(s, (struct sockaddr *)&a, sizeof(a))) {
fprintf(stderr, "Failed to connect to %s: %s\n", argv[1],
strerror(errno));
return -1;
}
while (1) {
int n;
if (recvmsg(s, &msg, 0) < 0) {
perror("Failed to receive message");
return -1;
}
if (!cmsg ||
cmsg->cmsg_len < CMSG_LEN(sizeof(int)) ||
cmsg->cmsg_len > CMSG_LEN(sizeof(int) * SCM_MAX_FD) ||
cmsg->cmsg_type != SCM_RIGHTS)
return -1;
n = cmsg->cmsg_len / CMSG_LEN(sizeof(int));
memcpy(fds, CMSG_DATA(cmsg), sizeof(int) * n);
switch (cmd) {
case INT_MAX:
return 0;
case TCP_REPAIR_ON:
case TCP_REPAIR_OFF:
case TCP_REPAIR_OFF_NO_WP:
for (i = 0; i < n; i++) {
if (setsockopt(fds[i], SOL_TCP, TCP_REPAIR,
&cmd, sizeof(int))) {
perror("Setting TCP_REPAIR");
return -1;
}
}
/* Confirm setting by echoing the command back */
if (send(s, &cmd, sizeof(int), 0) < 0) {
fprintf(stderr, "Reply to command %i: %s\n",
cmd, strerror(errno));
return -1;
}
break;
default:
fprintf(stderr, "Unsupported command 0x%04x\n", cmd);
return -1;
}
}
}
|