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/osdep.h" 19 #include "qemu-common.h" 20 #include "net/checksum.h" 21 22 #define PROTO_TCP 6 23 #define PROTO_UDP 17 24 25 uint32_t net_checksum_add_cont(int len, uint8_t *buf, int seq) 26 { 27 uint32_t sum = 0; 28 int i; 29 30 for (i = seq; i < seq + len; i++) { 31 if (i & 1) { 32 sum += (uint32_t)buf[i - seq]; 33 } else { 34 sum += (uint32_t)buf[i - seq] << 8; 35 } 36 } 37 return sum; 38 } 39 40 uint16_t net_checksum_finish(uint32_t sum) 41 { 42 while (sum>>16) 43 sum = (sum & 0xFFFF)+(sum >> 16); 44 return ~sum; 45 } 46 47 uint16_t net_checksum_tcpudp(uint16_t length, uint16_t proto, 48 uint8_t *addrs, uint8_t *buf) 49 { 50 uint32_t sum = 0; 51 52 sum += net_checksum_add(length, buf); // payload 53 sum += net_checksum_add(8, addrs); // src + dst address 54 sum += proto + length; // protocol & length 55 return net_checksum_finish(sum); 56 } 57 58 void net_checksum_calculate(uint8_t *data, int length) 59 { 60 int hlen, plen, proto, csum_offset; 61 uint16_t csum; 62 63 if ((data[14] & 0xf0) != 0x40) 64 return; /* not IPv4 */ 65 hlen = (data[14] & 0x0f) * 4; 66 plen = (data[16] << 8 | data[17]) - hlen; 67 proto = data[23]; 68 69 switch (proto) { 70 case PROTO_TCP: 71 csum_offset = 16; 72 break; 73 case PROTO_UDP: 74 csum_offset = 6; 75 break; 76 default: 77 return; 78 } 79 80 if (plen < csum_offset+2) 81 return; 82 83 data[14+hlen+csum_offset] = 0; 84 data[14+hlen+csum_offset+1] = 0; 85 csum = net_checksum_tcpudp(plen, proto, data+14+12, data+14+hlen); 86 data[14+hlen+csum_offset] = csum >> 8; 87 data[14+hlen+csum_offset+1] = csum & 0xff; 88 } 89 90 uint32_t 91 net_checksum_add_iov(const struct iovec *iov, const unsigned int iov_cnt, 92 uint32_t iov_off, uint32_t size) 93 { 94 size_t iovec_off, buf_off; 95 unsigned int i; 96 uint32_t res = 0; 97 uint32_t seq = 0; 98 99 iovec_off = 0; 100 buf_off = 0; 101 for (i = 0; i < iov_cnt && size; i++) { 102 if (iov_off < (iovec_off + iov[i].iov_len)) { 103 size_t len = MIN((iovec_off + iov[i].iov_len) - iov_off , size); 104 void *chunk_buf = iov[i].iov_base + (iov_off - iovec_off); 105 106 res += net_checksum_add_cont(len, chunk_buf, seq); 107 seq += len; 108 109 buf_off += len; 110 iov_off += len; 111 size -= len; 112 } 113 iovec_off += iov[i].iov_len; 114 } 115 return res; 116 } 117