115 lines
3.0 KiB
C
115 lines
3.0 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Author: Brett A C Sheffield <bacs@librecast.net>
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*
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* Kernel selftest for the IPv6 fragmentation regression which affected stable
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* kernels:
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*
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* https://lore.kernel.org/stable/aElivdUXqd1OqgMY@karahi.gladserv.com
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*
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* Commit: a18dfa9925b9 ("ipv6: save dontfrag in cork") was backported to stable
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* without some prerequisite commits.
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*
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* This caused a regression when sending IPv6 UDP packets by preventing
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* fragmentation and instead returning -1 (EMSGSIZE).
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*
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* This selftest demonstrates the issue by sending an IPv6 UDP packet to
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* localhost (::1) on the loopback interface from the autoconfigured link-local
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* address.
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*
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* sendmsg(2) returns bytes sent correctly on a working kernel, and returns -1
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* (EMSGSIZE) when the regression is present.
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*
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* The regression was not present in the mainline kernel, but add this test to
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* catch similar breakage in future.
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*/
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#define _GNU_SOURCE
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#include <error.h>
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#include <net/if.h>
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#include <netinet/in.h>
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#include <sched.h>
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#include <stdio.h>
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#include <sys/ioctl.h>
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#include <sys/socket.h>
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#include <unistd.h>
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#include "../kselftest.h"
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#define MTU 1500
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#define LARGER_THAN_MTU 8192
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static void setup(void)
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{
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struct ifreq ifr = {
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.ifr_name = "lo"
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};
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int ctl;
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/* we need to set MTU, so do this in a namespace to play nicely */
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if (unshare(CLONE_NEWNET) == -1)
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error(KSFT_FAIL, errno, "unshare");
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ctl = socket(AF_LOCAL, SOCK_STREAM, 0);
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if (ctl == -1)
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error(KSFT_FAIL, errno, "socket");
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/* ensure MTU is smaller than what we plan to send */
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ifr.ifr_mtu = MTU;
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if (ioctl(ctl, SIOCSIFMTU, &ifr) == -1)
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error(KSFT_FAIL, errno, "ioctl: set MTU");
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/* bring up interface */
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if (ioctl(ctl, SIOCGIFFLAGS, &ifr) == -1)
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error(KSFT_FAIL, errno, "ioctl SIOCGIFFLAGS");
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ifr.ifr_flags = ifr.ifr_flags | IFF_UP;
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if (ioctl(ctl, SIOCSIFFLAGS, &ifr) == -1)
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error(KSFT_FAIL, errno, "ioctl: bring interface up");
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if (close(ctl) == -1)
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error(KSFT_FAIL, errno, "close");
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}
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int main(void)
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{
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struct in6_addr addr = {
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.s6_addr[15] = 0x01, /* ::1 */
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};
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struct sockaddr_in6 sa = {
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.sin6_family = AF_INET6,
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.sin6_addr = addr,
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.sin6_port = htons(9) /* port 9/udp (DISCARD) */
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};
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static char buf[LARGER_THAN_MTU] = {0};
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struct iovec iov = { .iov_base = buf, .iov_len = sizeof(buf) };
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struct msghdr msg = {
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.msg_iov = &iov,
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.msg_iovlen = 1,
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.msg_name = (struct sockaddr *)&sa,
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.msg_namelen = sizeof(sa),
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};
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ssize_t rc;
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int s;
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printf("Testing IPv6 fragmentation\n");
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setup();
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s = socket(AF_INET6, SOCK_DGRAM, 0);
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send_again:
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rc = sendmsg(s, &msg, 0);
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if (rc == -1) {
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/* if interface wasn't ready, try again */
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if (errno == EADDRNOTAVAIL) {
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usleep(1000);
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goto send_again;
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}
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error(KSFT_FAIL, errno, "sendmsg");
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} else if (rc != LARGER_THAN_MTU) {
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error(KSFT_FAIL, errno, "sendmsg returned %zi, expected %i",
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rc, LARGER_THAN_MTU);
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}
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printf("[PASS] sendmsg() returned %zi\n", rc);
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if (close(s) == -1)
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error(KSFT_FAIL, errno, "close");
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return KSFT_PASS;
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}
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