--- /dev/null
+// SPDX-License-Identifier: GPL-2.0
+
+/* Open a tun device.
+ *
+ * [modifications: use IFF_NAPI_FRAGS, add sk filter]
+ *
+ * Expects the device to have been configured previously, e.g.:
+ * sudo ip tuntap add name tap1 mode tap
+ * sudo ip link set tap1 up
+ * sudo ip link set dev tap1 addr 02:00:00:00:00:01
+ * sudo ip -6 addr add fdab::1 peer fdab::2 dev tap1 nodad
+ *
+ * And to avoid premature pskb_may_pull:
+ *
+ * sudo ethtool -K tap1 gro off
+ * sudo bash -c 'echo 0 > /proc/sys/net/ipv4/ip_early_demux'
+ */
+
+#define _GNU_SOURCE
+
+#include <arpa/inet.h>
+#include <errno.h>
+#include <error.h>
+#include <fcntl.h>
+#include <getopt.h>
+#include <linux/filter.h>
+#include <linux/if.h>
+#include <linux/if_packet.h>
+#include <linux/if_tun.h>
+#include <linux/ipv6.h>
+#include <netinet/if_ether.h>
+#include <netinet/in.h>
+#include <netinet/ip.h>
+#include <netinet/ip6.h>
+#include <netinet/udp.h>
+#include <poll.h>
+#include <signal.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <sys/socket.h>
+#include <sys/poll.h>
+#include <sys/types.h>
+#include <sys/uio.h>
+#include <unistd.h>
+
+static bool cfg_do_filter;
+static bool cfg_do_frags;
+static int cfg_dst_port = 8000;
+static char *cfg_ifname;
+
+static int tun_open(const char *tun_name)
+{
+ struct ifreq ifr = {0};
+ int fd, ret;
+
+ fd = open("/dev/net/tun", O_RDWR);
+ if (fd == -1)
+ error(1, errno, "open /dev/net/tun");
+
+ ifr.ifr_flags = IFF_TAP;
+ if (cfg_do_frags)
+ ifr.ifr_flags |= IFF_NAPI | IFF_NAPI_FRAGS;
+
+ strncpy(ifr.ifr_name, tun_name, IFNAMSIZ - 1);
+
+ ret = ioctl(fd, TUNSETIFF, &ifr);
+ if (ret)
+ error(1, ret, "ioctl TUNSETIFF");
+
+ return fd;
+}
+
+static void sk_set_filter(int fd)
+{
+ const int offset_proto = offsetof(struct ip6_hdr, ip6_nxt);
+ const int offset_dport = sizeof(struct ip6_hdr) + offsetof(struct udphdr, dest);
+
+ /* Filter UDP packets with destination port cfg_dst_port */
+ struct sock_filter filter_code[] = {
+ BPF_STMT(BPF_LD + BPF_B + BPF_ABS, SKF_AD_OFF + SKF_AD_PKTTYPE),
+ BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, PACKET_HOST, 0, 4),
+ BPF_STMT(BPF_LD + BPF_B + BPF_ABS, SKF_NET_OFF + offset_proto),
+ BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 0, 2),
+ BPF_STMT(BPF_LD + BPF_H + BPF_ABS, SKF_NET_OFF + offset_dport),
+ BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, cfg_dst_port, 1, 0),
+ BPF_STMT(BPF_RET + BPF_K, 0),
+ BPF_STMT(BPF_RET + BPF_K, 0xFFFF),
+ };
+
+ struct sock_fprog filter = {
+ sizeof(filter_code) / sizeof(filter_code[0]),
+ filter_code,
+ };
+
+ if (setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, &filter, sizeof(filter)))
+ error(1, errno, "setsockopt attach filter");
+}
+
+static int raw_open(void)
+{
+ int fd;
+
+ fd = socket(PF_INET6, SOCK_RAW, IPPROTO_UDP);
+ if (fd == -1)
+ error(1, errno, "socket raw (udp)");
+
+ if (cfg_do_filter)
+ sk_set_filter(fd);
+
+ return fd;
+}
+
+static void tun_write(int fd)
+{
+ const char eth_src[] = { 0x02, 0x00, 0x00, 0x00, 0x00, 0x02 };
+ const char eth_dst[] = { 0x02, 0x00, 0x00, 0x00, 0x00, 0x01 };
+ struct tun_pi pi = {0};
+ struct ipv6hdr ip6h = {0};
+ struct udphdr uh = {0};
+ struct ethhdr eth = {0};
+ uint32_t payload;
+ struct iovec iov[5];
+ int ret;
+
+ pi.proto = htons(ETH_P_IPV6);
+
+ memcpy(eth.h_source, eth_src, sizeof(eth_src));
+ memcpy(eth.h_dest, eth_dst, sizeof(eth_dst));
+ eth.h_proto = htons(ETH_P_IPV6);
+
+ ip6h.version = 6;
+ ip6h.payload_len = htons(sizeof(uh) + sizeof(uint32_t));
+ ip6h.nexthdr = IPPROTO_UDP;
+ ip6h.hop_limit = 8;
+ if (inet_pton(AF_INET6, "fdab::2", &ip6h.saddr) != 1)
+ error(1, errno, "inet_pton src");
+ if (inet_pton(AF_INET6, "fdab::1", &ip6h.daddr) != 1)
+ error(1, errno, "inet_pton src");
+
+ uh.source = htons(8000);
+ uh.dest = htons(cfg_dst_port);
+ uh.len = ip6h.payload_len;
+ uh.check = 0;
+
+ payload = htonl(0xABABABAB); /* Covered in IPv6 length */
+
+ iov[0].iov_base = π
+ iov[0].iov_len = sizeof(pi);
+ iov[1].iov_base = ð
+ iov[1].iov_len = sizeof(eth);
+ iov[2].iov_base = &ip6h;
+ iov[2].iov_len = sizeof(ip6h);
+ iov[3].iov_base = &uh;
+ iov[3].iov_len = sizeof(uh);
+ iov[4].iov_base = &payload;
+ iov[4].iov_len = sizeof(payload);
+
+ ret = writev(fd, iov, sizeof(iov) / sizeof(iov[0]));
+ if (ret <= 0)
+ error(1, errno, "writev");
+}
+
+static void raw_read(int fd)
+{
+ struct timeval tv = { .tv_usec = 100 * 1000 };
+ struct msghdr msg = {0};
+ struct iovec iov[2];
+ struct udphdr uh;
+ uint32_t payload[2];
+ int ret;
+
+ if (setsockopt(fd, SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof(tv)))
+ error(1, errno, "setsockopt rcvtimeo udp");
+
+ iov[0].iov_base = &uh;
+ iov[0].iov_len = sizeof(uh);
+
+ iov[1].iov_base = payload;
+ iov[1].iov_len = sizeof(payload);
+
+ msg.msg_iov = iov;
+ msg.msg_iovlen = sizeof(iov) / sizeof(iov[0]);
+
+ ret = recvmsg(fd, &msg, 0);
+ if (ret <= 0)
+ error(1, errno, "read raw");
+ if (ret != sizeof(uh) + sizeof(payload[0]))
+ error(1, errno, "read raw: len=%d\n", ret);
+
+ fprintf(stderr, "raw recv: 0x%x\n", payload[0]);
+}
+
+static void parse_opts(int argc, char **argv)
+{
+ int c;
+
+ while ((c = getopt(argc, argv, "fFi:")) != -1) {
+ switch (c) {
+ case 'f':
+ cfg_do_filter = true;
+ printf("bpf filter enabled\n");
+ break;
+ case 'F':
+ cfg_do_frags = true;
+ printf("napi frags mode enabled\n");
+ break;
+ case 'i':
+ cfg_ifname = optarg;
+ break;
+ default:
+ error(1, 0, "unknown option %c", optopt);
+ break;
+ }
+ }
+
+ if (!cfg_ifname)
+ error(1, 0, "must specify tap interface name (-i)");
+}
+
+int main(int argc, char **argv)
+{
+ int fdt, fdr;
+
+ parse_opts(argc, argv);
+
+ fdr = raw_open();
+ fdt = tun_open(cfg_ifname);
+
+ tun_write(fdt);
+ raw_read(fdr);
+
+ if (close(fdt))
+ error(1, errno, "close tun");
+ if (close(fdr))
+ error(1, errno, "close udp");
+
+ fprintf(stderr, "OK\n");
+ return 0;
+}
+
projects / thirdparty / kernel / linux.git / commitdiff
