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, int csum_flag) 61 { 62 int mac_hdr_len, ip_len; 63 struct ip_header *ip; 64 uint16_t csum; 65 66 /* 67 * Note: We cannot assume "data" is aligned, so the all code uses 68 * some macros that take care of possible unaligned access for 69 * struct members (just in case). 70 */ 71 72 /* Ensure we have at least an Eth header */ 73 if (length < sizeof(struct eth_header)) { 74 return; 75 } 76 77 /* Handle the optionnal VLAN headers */ 78 switch (lduw_be_p(&PKT_GET_ETH_HDR(data)->h_proto)) { 79 case ETH_P_VLAN: 80 mac_hdr_len = sizeof(struct eth_header) + 81 sizeof(struct vlan_header); 82 break; 83 case ETH_P_DVLAN: 84 if (lduw_be_p(&PKT_GET_VLAN_HDR(data)->h_proto) == ETH_P_VLAN) { 85 mac_hdr_len = sizeof(struct eth_header) + 86 2 * sizeof(struct vlan_header); 87 } else { 88 mac_hdr_len = sizeof(struct eth_header) + 89 sizeof(struct vlan_header); 90 } 91 break; 92 default: 93 mac_hdr_len = sizeof(struct eth_header); 94 break; 95 } 96 97 length -= mac_hdr_len; 98 99 /* Now check we have an IP header (with an optionnal VLAN header) */ 100 if (length < sizeof(struct ip_header)) { 101 return; 102 } 103 104 ip = (struct ip_header *)(data + mac_hdr_len); 105 106 if (IP_HEADER_VERSION(ip) != IP_HEADER_VERSION_4) { 107 return; /* not IPv4 */ 108 } 109 110 /* Calculate IP checksum */ 111 if (csum_flag & CSUM_IP) { 112 stw_he_p(&ip->ip_sum, 0); 113 csum = net_raw_checksum((uint8_t *)ip, IP_HDR_GET_LEN(ip)); 114 stw_be_p(&ip->ip_sum, csum); 115 } 116 117 if (IP4_IS_FRAGMENT(ip)) { 118 return; /* a fragmented IP packet */ 119 } 120 121 ip_len = lduw_be_p(&ip->ip_len); 122 123 /* Last, check that we have enough data for the all IP frame */ 124 if (length < ip_len) { 125 return; 126 } 127 128 ip_len -= IP_HDR_GET_LEN(ip); 129 130 switch (ip->ip_p) { 131 case IP_PROTO_TCP: 132 { 133 if (!(csum_flag & CSUM_TCP)) { 134 return; 135 } 136 137 tcp_header *tcp = (tcp_header *)(ip + 1); 138 139 if (ip_len < sizeof(tcp_header)) { 140 return; 141 } 142 143 /* Set csum to 0 */ 144 stw_he_p(&tcp->th_sum, 0); 145 146 csum = net_checksum_tcpudp(ip_len, ip->ip_p, 147 (uint8_t *)&ip->ip_src, 148 (uint8_t *)tcp); 149 150 /* Store computed csum */ 151 stw_be_p(&tcp->th_sum, csum); 152 153 break; 154 } 155 case IP_PROTO_UDP: 156 { 157 if (!(csum_flag & CSUM_UDP)) { 158 return; 159 } 160 161 udp_header *udp = (udp_header *)(ip + 1); 162 163 if (ip_len < sizeof(udp_header)) { 164 return; 165 } 166 167 /* Set csum to 0 */ 168 stw_he_p(&udp->uh_sum, 0); 169 170 csum = net_checksum_tcpudp(ip_len, ip->ip_p, 171 (uint8_t *)&ip->ip_src, 172 (uint8_t *)udp); 173 174 /* Store computed csum */ 175 stw_be_p(&udp->uh_sum, csum); 176 177 break; 178 } 179 default: 180 /* Can't handle any other protocol */ 181 break; 182 } 183 } 184 185 uint32_t 186 net_checksum_add_iov(const struct iovec *iov, const unsigned int iov_cnt, 187 uint32_t iov_off, uint32_t size, uint32_t csum_offset) 188 { 189 size_t iovec_off, buf_off; 190 unsigned int i; 191 uint32_t res = 0; 192 193 iovec_off = 0; 194 buf_off = 0; 195 for (i = 0; i < iov_cnt && size; i++) { 196 if (iov_off < (iovec_off + iov[i].iov_len)) { 197 size_t len = MIN((iovec_off + iov[i].iov_len) - iov_off , size); 198 void *chunk_buf = iov[i].iov_base + (iov_off - iovec_off); 199 200 res += net_checksum_add_cont(len, chunk_buf, csum_offset); 201 csum_offset += len; 202 203 buf_off += len; 204 iov_off += len; 205 size -= len; 206 } 207 iovec_off += iov[i].iov_len; 208 } 209 return res; 210 } 211