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Merge branch 'support-skf_net_off-and-skf_ll_off-on-skb-frags'
Willem de Bruijn says:
====================
support SKF_NET_OFF and SKF_LL_OFF on skb frags
From: Willem de Bruijn <willemb@google.com>
Address a longstanding issue that may lead to missed packets
depending on system configuration.
Ensure that reading from packet contents works regardless of skb
geometry, also when using the special SKF_.. negative offsets to
offset from L2 or L3 header.
Patch 2 is the selftest for the fix.
v2->v3
- do not remove bpf_internal_load_pointer_neg_helper, because it
is still used in the sparc32 JIT
v1->v2
- introduce bfp_skb_load_helper_convert_offset to avoid open
coding
- selftest: add comment why early demux must be disabled
v2: https://lore.kernel.org/netdev/20250404142633.1955847-1-willemdebruijn.kernel@gmail.com/
v1: https://lore.kernel.org/netdev/20250403140846.1268564-1-willemdebruijn.kernel@gmail.com/
====================
Link: https://patch.msgid.link/20250408132833.195491-1-willemdebruijn.kernel@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>- Loading branch information
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,244 @@ | ||
| // SPDX-License-Identifier: GPL-2.0 | ||
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||
| /* 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' | ||
| */ | ||
|
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||
| #define _GNU_SOURCE | ||
|
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||
| #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; | ||
|
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||
| static int tun_open(const char *tun_name) | ||
| { | ||
| struct ifreq ifr = {0}; | ||
| int fd, ret; | ||
|
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||
| fd = open("/dev/net/tun", O_RDWR); | ||
| if (fd == -1) | ||
| error(1, errno, "open /dev/net/tun"); | ||
|
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||
| ifr.ifr_flags = IFF_TAP; | ||
| if (cfg_do_frags) | ||
| ifr.ifr_flags |= IFF_NAPI | IFF_NAPI_FRAGS; | ||
|
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||
| strncpy(ifr.ifr_name, tun_name, IFNAMSIZ - 1); | ||
|
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||
| ret = ioctl(fd, TUNSETIFF, &ifr); | ||
| if (ret) | ||
| error(1, ret, "ioctl TUNSETIFF"); | ||
|
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||
| return fd; | ||
| } | ||
|
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||
| 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, | ||
| }; | ||
|
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||
| if (setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, &filter, sizeof(filter))) | ||
| error(1, errno, "setsockopt attach filter"); | ||
| } | ||
|
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||
| static int raw_open(void) | ||
| { | ||
| int fd; | ||
|
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| fd = socket(PF_INET6, SOCK_RAW, IPPROTO_UDP); | ||
| if (fd == -1) | ||
| error(1, errno, "socket raw (udp)"); | ||
|
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| if (cfg_do_filter) | ||
| sk_set_filter(fd); | ||
|
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| return fd; | ||
| } | ||
|
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||
| 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; | ||
|
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| pi.proto = htons(ETH_P_IPV6); | ||
|
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| 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); | ||
|
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| 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"); | ||
|
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||
| uh.source = htons(8000); | ||
| uh.dest = htons(cfg_dst_port); | ||
| uh.len = ip6h.payload_len; | ||
| uh.check = 0; | ||
|
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| payload = htonl(0xABABABAB); /* Covered in IPv6 length */ | ||
|
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||
| 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); | ||
|
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||
| ret = writev(fd, iov, sizeof(iov) / sizeof(iov[0])); | ||
| if (ret <= 0) | ||
| error(1, errno, "writev"); | ||
| } | ||
|
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||
| 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; | ||
|
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| if (setsockopt(fd, SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof(tv))) | ||
| error(1, errno, "setsockopt rcvtimeo udp"); | ||
|
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| iov[0].iov_base = &uh; | ||
| iov[0].iov_len = sizeof(uh); | ||
|
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| iov[1].iov_base = payload; | ||
| iov[1].iov_len = sizeof(payload); | ||
|
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| msg.msg_iov = iov; | ||
| msg.msg_iovlen = sizeof(iov) / sizeof(iov[0]); | ||
|
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| 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); | ||
|
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| fprintf(stderr, "raw recv: 0x%x\n", payload[0]); | ||
| } | ||
|
|
||
| static void parse_opts(int argc, char **argv) | ||
| { | ||
| int c; | ||
|
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||
| 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)"); | ||
| } | ||
|
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||
| int main(int argc, char **argv) | ||
| { | ||
| int fdt, fdr; | ||
|
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| parse_opts(argc, argv); | ||
|
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| fdr = raw_open(); | ||
| fdt = tun_open(cfg_ifname); | ||
|
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| tun_write(fdt); | ||
| raw_read(fdr); | ||
|
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| if (close(fdt)) | ||
| error(1, errno, "close tun"); | ||
| if (close(fdr)) | ||
| error(1, errno, "close udp"); | ||
|
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||
| fprintf(stderr, "OK\n"); | ||
| return 0; | ||
| } | ||
|
|
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