1/*
2 * Copyright 2014 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 *
16 * ring.c - packet ring buffer functions
17 */
18
19#include <errno.h>
20#include <string.h>
21#include <arpa/inet.h>
22#include <sys/socket.h>
23#include <sys/mman.h>
24#include <linux/if.h>
25#include <linux/if_packet.h>
26
27#include "logging.h"
28#include "ring.h"
29#include "translate.h"
30#include "tun.h"
31
32int ring_create(struct tun_data *tunnel) {
33  int packetsock = socket(AF_PACKET, SOCK_DGRAM, htons(ETH_P_IPV6));
34  if (packetsock < 0) {
35    logmsg(ANDROID_LOG_FATAL, "packet socket failed: %s", strerror(errno));
36    return -1;
37  }
38
39  int ver = TPACKET_V2;
40  if (setsockopt(packetsock, SOL_PACKET, PACKET_VERSION, (void *) &ver, sizeof(ver))) {
41    logmsg(ANDROID_LOG_FATAL, "setsockopt(PACKET_VERSION, %d) failed: %s", ver, strerror(errno));
42    return -1;
43  }
44
45  int on = 1;
46  if (setsockopt(packetsock, SOL_PACKET, PACKET_LOSS, (void *) &on, sizeof(on))) {
47    logmsg(ANDROID_LOG_WARN, "PACKET_LOSS failed: %s", strerror(errno));
48  }
49
50  struct packet_ring *ring = &tunnel->ring;
51  ring->numblocks = TP_NUM_BLOCKS;
52
53  int total_frames = TP_FRAMES * ring->numblocks;
54
55  struct tpacket_req req = {
56      .tp_frame_size = TP_FRAME_SIZE,  // Frame size.
57      .tp_block_size = TP_BLOCK_SIZE,  // Frames per block.
58      .tp_block_nr = ring->numblocks,  // Number of blocks.
59      .tp_frame_nr = total_frames,     // Total frames.
60  };
61
62  if (setsockopt(packetsock, SOL_PACKET, PACKET_RX_RING, &req, sizeof(req)) < 0) {
63    logmsg(ANDROID_LOG_FATAL, "PACKET_RX_RING failed: %s", strerror(errno));
64    return -1;
65  }
66
67  size_t buflen = TP_BLOCK_SIZE * ring->numblocks;
68  ring->base = mmap(NULL, buflen, PROT_READ|PROT_WRITE, MAP_SHARED|MAP_LOCKED|MAP_POPULATE,
69                    packetsock, 0);
70  if (ring->base == MAP_FAILED) {
71    logmsg(ANDROID_LOG_FATAL, "mmap %lu failed: %s", buflen, strerror(errno));
72    return -1;
73  }
74
75  ring->block = 0;
76  ring->slot = 0;
77  ring->numslots = TP_BLOCK_SIZE / TP_FRAME_SIZE;
78  ring->next = (struct tpacket2_hdr *) ring->base;
79
80  logmsg(ANDROID_LOG_INFO, "Using ring buffer with %d frames (%d bytes) at %p",
81         total_frames, buflen, ring->base);
82
83  return packetsock;
84}
85
86/* function: ring_advance
87 * advances to the next position in the packet ring
88 * ring - packet ring buffer
89 */
90static struct tpacket2_hdr* ring_advance(struct packet_ring *ring) {
91  uint8_t *next = (uint8_t *) ring->next;
92
93  ring->slot++;
94  next += TP_FRAME_SIZE;
95
96  if (ring->slot == ring->numslots) {
97    ring->slot = 0;
98    ring->block++;
99
100    if (ring->block < ring->numblocks) {
101      next += TP_FRAME_GAP;
102    } else {
103      ring->block = 0;
104      next = (uint8_t *) ring->base;
105    }
106  }
107
108  ring->next = (struct tpacket2_hdr *) next;
109  return ring->next;
110}
111
112/* function: ring_read
113 * reads a packet from the ring buffer and translates it
114 * read_fd  - file descriptor to read original packet from
115 * write_fd - file descriptor to write translated packet to
116 * to_ipv6  - whether the packet is to be translated to ipv6 or ipv4
117 */
118void ring_read(struct packet_ring *ring, int write_fd, int to_ipv6) {
119  struct tpacket2_hdr *tp = ring->next;
120  if (tp->tp_status & TP_STATUS_USER) {
121    uint8_t *packet = ((uint8_t *) tp) + tp->tp_net;
122    translate_packet(write_fd, to_ipv6, packet, tp->tp_len);
123    tp->tp_status = TP_STATUS_KERNEL;
124    tp = ring_advance(ring);
125  }
126}
127