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 "net/checksum.h" 20 #include "net/eth.h" 21 22 uint32_t net_checksum_add_cont(int len, uint8_t *buf, int seq) 23 { 24 uint32_t sum1 = 0, sum2 = 0; 25 int i; 26 27 for (i = 0; i < len - 1; i += 2) { 28 sum1 += (uint32_t)buf[i]; 29 sum2 += (uint32_t)buf[i + 1]; 30 } 31 if (i < len) { 32 sum1 += (uint32_t)buf[i]; 33 } 34 35 if (seq & 1) { 36 return sum1 + (sum2 << 8); 37 } else { 38 return sum2 + (sum1 << 8); 39 } 40 } 41 42 uint16_t net_checksum_finish(uint32_t sum) 43 { 44 while (sum>>16) 45 sum = (sum & 0xFFFF)+(sum >> 16); 46 return ~sum; 47 } 48 49 uint16_t net_checksum_tcpudp(uint16_t length, uint16_t proto, 50 uint8_t *addrs, uint8_t *buf) 51 { 52 uint32_t sum = 0; 53 54 sum += net_checksum_add(length, buf); // payload 55 sum += net_checksum_add(8, addrs); // src + dst address 56 sum += proto + length; // protocol & length 57 return net_checksum_finish(sum); 58 } 59 60 void net_checksum_calculate(uint8_t *data, int length) 61 { 62 int mac_hdr_len, ip_len; 63 struct ip_header *ip; 64 65 /* 66 * Note: We cannot assume "data" is aligned, so the all code uses 67 * some macros that take care of possible unaligned access for 68 * struct members (just in case). 69 */ 70 71 /* Ensure we have at least an Eth header */ 72 if (length < sizeof(struct eth_header)) { 73 return; 74 } 75 76 /* Handle the optionnal VLAN headers */ 77 switch (lduw_be_p(&PKT_GET_ETH_HDR(data)->h_proto)) { 78 case ETH_P_VLAN: 79 mac_hdr_len = sizeof(struct eth_header) + 80 sizeof(struct vlan_header); 81 break; 82 case ETH_P_DVLAN: 83 if (lduw_be_p(&PKT_GET_VLAN_HDR(data)->h_proto) == ETH_P_VLAN) { 84 mac_hdr_len = sizeof(struct eth_header) + 85 2 * sizeof(struct vlan_header); 86 } else { 87 mac_hdr_len = sizeof(struct eth_header) + 88 sizeof(struct vlan_header); 89 } 90 break; 91 default: 92 mac_hdr_len = sizeof(struct eth_header); 93 break; 94 } 95 96 length -= mac_hdr_len; 97 98 /* Now check we have an IP header (with an optionnal VLAN header) */ 99 if (length < sizeof(struct ip_header)) { 100 return; 101 } 102 103 ip = (struct ip_header *)(data + mac_hdr_len); 104 105 if (IP_HEADER_VERSION(ip) != IP_HEADER_VERSION_4) { 106 return; /* not IPv4 */ 107 } 108 109 ip_len = lduw_be_p(&ip->ip_len); 110 111 /* Last, check that we have enough data for the all IP frame */ 112 if (length < ip_len) { 113 return; 114 } 115 116 ip_len -= IP_HDR_GET_LEN(ip); 117 118 switch (ip->ip_p) { 119 case IP_PROTO_TCP: 120 { 121 uint16_t csum; 122 tcp_header *tcp = (tcp_header *)(ip + 1); 123 124 if (ip_len < sizeof(tcp_header)) { 125 return; 126 } 127 128 /* Set csum to 0 */ 129 stw_he_p(&tcp->th_sum, 0); 130 131 csum = net_checksum_tcpudp(ip_len, ip->ip_p, 132 (uint8_t *)&ip->ip_src, 133 (uint8_t *)tcp); 134 135 /* Store computed csum */ 136 stw_be_p(&tcp->th_sum, csum); 137 138 break; 139 } 140 case IP_PROTO_UDP: 141 { 142 uint16_t csum; 143 udp_header *udp = (udp_header *)(ip + 1); 144 145 if (ip_len < sizeof(udp_header)) { 146 return; 147 } 148 149 /* Set csum to 0 */ 150 stw_he_p(&udp->uh_sum, 0); 151 152 csum = net_checksum_tcpudp(ip_len, ip->ip_p, 153 (uint8_t *)&ip->ip_src, 154 (uint8_t *)udp); 155 156 /* Store computed csum */ 157 stw_be_p(&udp->uh_sum, csum); 158 159 break; 160 } 161 default: 162 /* Can't handle any other protocol */ 163 break; 164 } 165 } 166 167 uint32_t 168 net_checksum_add_iov(const struct iovec *iov, const unsigned int iov_cnt, 169 uint32_t iov_off, uint32_t size, uint32_t csum_offset) 170 { 171 size_t iovec_off, buf_off; 172 unsigned int i; 173 uint32_t res = 0; 174 175 iovec_off = 0; 176 buf_off = 0; 177 for (i = 0; i < iov_cnt && size; i++) { 178 if (iov_off < (iovec_off + iov[i].iov_len)) { 179 size_t len = MIN((iovec_off + iov[i].iov_len) - iov_off , size); 180 void *chunk_buf = iov[i].iov_base + (iov_off - iovec_off); 181 182 res += net_checksum_add_cont(len, chunk_buf, csum_offset); 183 csum_offset += len; 184 185 buf_off += len; 186 iov_off += len; 187 size -= len; 188 } 189 iovec_off += iov[i].iov_len; 190 } 191 return res; 192 } 193