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/*
* Copyright 2014 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* ring.c - packet ring buffer functions
*/
#include <errno.h>
#include <string.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <sys/mman.h>
#include <linux/if.h>
#include <linux/if_packet.h>
#include "logging.h"
#include "ring.h"
#include "translate.h"
#include "tun.h"
int ring_create(struct tun_data *tunnel) {
int packetsock = socket(AF_PACKET, SOCK_DGRAM, htons(ETH_P_IPV6));
if (packetsock < 0) {
logmsg(ANDROID_LOG_FATAL, "packet socket failed: %s", strerror(errno));
return -1;
}
int ver = TPACKET_V2;
if (setsockopt(packetsock, SOL_PACKET, PACKET_VERSION, (void *) &ver, sizeof(ver))) {
logmsg(ANDROID_LOG_FATAL, "setsockopt(PACKET_VERSION, %d) failed: %s", ver, strerror(errno));
return -1;
}
int on = 1;
if (setsockopt(packetsock, SOL_PACKET, PACKET_LOSS, (void *) &on, sizeof(on))) {
logmsg(ANDROID_LOG_WARN, "PACKET_LOSS failed: %s", strerror(errno));
}
struct packet_ring *ring = &tunnel->ring;
ring->numblocks = TP_NUM_BLOCKS;
int total_frames = TP_FRAMES * ring->numblocks;
struct tpacket_req req = {
.tp_frame_size = TP_FRAME_SIZE, // Frame size.
.tp_block_size = TP_BLOCK_SIZE, // Frames per block.
.tp_block_nr = ring->numblocks, // Number of blocks.
.tp_frame_nr = total_frames, // Total frames.
};
if (setsockopt(packetsock, SOL_PACKET, PACKET_RX_RING, &req, sizeof(req)) < 0) {
logmsg(ANDROID_LOG_FATAL, "PACKET_RX_RING failed: %s", strerror(errno));
return -1;
}
size_t buflen = TP_BLOCK_SIZE * ring->numblocks;
ring->base = mmap(NULL, buflen, PROT_READ|PROT_WRITE, MAP_SHARED|MAP_LOCKED|MAP_POPULATE,
packetsock, 0);
if (ring->base == MAP_FAILED) {
logmsg(ANDROID_LOG_FATAL, "mmap %lu failed: %s", buflen, strerror(errno));
return -1;
}
ring->block = 0;
ring->slot = 0;
ring->numslots = TP_BLOCK_SIZE / TP_FRAME_SIZE;
ring->next = (struct tpacket2_hdr *) ring->base;
logmsg(ANDROID_LOG_INFO, "Using ring buffer with %d frames (%d bytes) at %p",
total_frames, buflen, ring->base);
return packetsock;
}
/* function: ring_advance
* advances to the next position in the packet ring
* ring - packet ring buffer
*/
static struct tpacket2_hdr* ring_advance(struct packet_ring *ring) {
uint8_t *next = (uint8_t *) ring->next;
ring->slot++;
next += TP_FRAME_SIZE;
if (ring->slot == ring->numslots) {
ring->slot = 0;
ring->block++;
if (ring->block < ring->numblocks) {
next += TP_FRAME_GAP;
} else {
ring->block = 0;
next = (uint8_t *) ring->base;
}
}
ring->next = (struct tpacket2_hdr *) next;
return ring->next;
}
/* function: ring_read
* reads a packet from the ring buffer and translates it
* read_fd - file descriptor to read original packet from
* write_fd - file descriptor to write translated packet to
* to_ipv6 - whether the packet is to be translated to ipv6 or ipv4
*/
void ring_read(struct packet_ring *ring, int write_fd, int to_ipv6) {
struct tpacket2_hdr *tp = ring->next;
uint16_t val = TP_CSUM_NONE;
if (tp->tp_status & TP_STATUS_USER) {
//We expect only GRO coalesced packets to have TP_STATUS_CSUMNOTREADY
//(ip_summed = CHECKSUM_PARTIAL) in this path. Note that these packets have already gone
//through checksum validation in GRO engine. CHECKSUM_PARTIAL is defined to be 3 while
//CHECKSUM_UNNECESSARY is defined to be 1.
//Kernel only checks for CHECKSUM_UNNECESSARY (TP_CSUM_UNNECESSARY) bit while processing a
//packet, so its ok to pass only this bit rather than the full ip_summed field.
if ((tp->tp_status & TP_STATUS_CSUMNOTREADY) || (tp->tp_status & TP_STATUS_CSUM_UNNECESSARY)) {
val = TP_CSUM_UNNECESSARY;
}
uint8_t *packet = ((uint8_t *) tp) + tp->tp_net;
translate_packet(write_fd, to_ipv6, packet, tp->tp_len, val);
tp->tp_status = TP_STATUS_KERNEL;
tp = ring_advance(ring);
}
}
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