1 /* 2 * IP checksumming functions. 3 * (c) 2008 Gerd Hoffmann <kraxel@redhat.com> 4 * 5 * This program is free software; you can redistribute it and/or modify 6 * it under the terms of the GNU General Public License as published by 7 * the Free Software Foundation; under version 2 or later of the License. 8 * 9 * This program is distributed in the hope that it will be useful, 10 * but WITHOUT ANY WARRANTY; without even the implied warranty of 11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 12 * GNU General Public License for more details. 13 * 14 * You should have received a copy of the GNU General Public License 15 * along with this program; if not, see <http://www.gnu.org/licenses/>. 16 */ 17 18 #include "qemu-common.h" 19 #include "net/checksum.h" 20 21 #define PROTO_TCP 6 22 #define PROTO_UDP 17 23 24 uint32_t net_checksum_add_cont(int len, uint8_t *buf, int seq) 25 { 26 uint32_t sum = 0; 27 int i; 28 29 for (i = seq; i < seq + len; i++) { 30 if (i & 1) { 31 sum += (uint32_t)buf[i - seq]; 32 } else { 33 sum += (uint32_t)buf[i - seq] << 8; 34 } 35 } 36 return sum; 37 } 38 39 uint16_t net_checksum_finish(uint32_t sum) 40 { 41 while (sum>>16) 42 sum = (sum & 0xFFFF)+(sum >> 16); 43 return ~sum; 44 } 45 46 uint16_t net_checksum_tcpudp(uint16_t length, uint16_t proto, 47 uint8_t *addrs, uint8_t *buf) 48 { 49 uint32_t sum = 0; 50 51 sum += net_checksum_add(length, buf); // payload 52 sum += net_checksum_add(8, addrs); // src + dst address 53 sum += proto + length; // protocol & length 54 return net_checksum_finish(sum); 55 } 56 57 void net_checksum_calculate(uint8_t *data, int length) 58 { 59 int hlen, plen, proto, csum_offset; 60 uint16_t csum; 61 62 if ((data[14] & 0xf0) != 0x40) 63 return; /* not IPv4 */ 64 hlen = (data[14] & 0x0f) * 4; 65 plen = (data[16] << 8 | data[17]) - hlen; 66 proto = data[23]; 67 68 switch (proto) { 69 case PROTO_TCP: 70 csum_offset = 16; 71 break; 72 case PROTO_UDP: 73 csum_offset = 6; 74 break; 75 default: 76 return; 77 } 78 79 if (plen < csum_offset+2) 80 return; 81 82 data[14+hlen+csum_offset] = 0; 83 data[14+hlen+csum_offset+1] = 0; 84 csum = net_checksum_tcpudp(plen, proto, data+14+12, data+14+hlen); 85 data[14+hlen+csum_offset] = csum >> 8; 86 data[14+hlen+csum_offset+1] = csum & 0xff; 87 } 88 89 uint32_t 90 net_checksum_add_iov(const struct iovec *iov, const unsigned int iov_cnt, 91 uint32_t iov_off, uint32_t size) 92 { 93 size_t iovec_off, buf_off; 94 unsigned int i; 95 uint32_t res = 0; 96 uint32_t seq = 0; 97 98 iovec_off = 0; 99 buf_off = 0; 100 for (i = 0; i < iov_cnt && size; i++) { 101 if (iov_off < (iovec_off + iov[i].iov_len)) { 102 size_t len = MIN((iovec_off + iov[i].iov_len) - iov_off , size); 103 void *chunk_buf = iov[i].iov_base + (iov_off - iovec_off); 104 105 res += net_checksum_add_cont(len, chunk_buf, seq); 106 seq += len; 107 108 buf_off += len; 109 iov_off += len; 110 size -= len; 111 } 112 iovec_off += iov[i].iov_len; 113 } 114 return res; 115 } 116