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 #include "net/eth.h" 22 23 uint32_t net_checksum_add_cont(int len, uint8_t *buf, int seq) 24 { 25 uint32_t sum1 = 0, sum2 = 0; 26 int i; 27 28 for (i = 0; i < len - 1; i += 2) { 29 sum1 += (uint32_t)buf[i]; 30 sum2 += (uint32_t)buf[i + 1]; 31 } 32 if (i < len) { 33 sum1 += (uint32_t)buf[i]; 34 } 35 36 if (seq & 1) { 37 return sum1 + (sum2 << 8); 38 } else { 39 return sum2 + (sum1 << 8); 40 } 41 } 42 43 uint16_t net_checksum_finish(uint32_t sum) 44 { 45 while (sum>>16) 46 sum = (sum & 0xFFFF)+(sum >> 16); 47 return ~sum; 48 } 49 50 uint16_t net_checksum_tcpudp(uint16_t length, uint16_t proto, 51 uint8_t *addrs, uint8_t *buf) 52 { 53 uint32_t sum = 0; 54 55 sum += net_checksum_add(length, buf); // payload 56 sum += net_checksum_add(8, addrs); // src + dst address 57 sum += proto + length; // protocol & length 58 return net_checksum_finish(sum); 59 } 60 61 void net_checksum_calculate(uint8_t *data, int length) 62 { 63 int mac_hdr_len, ip_len; 64 struct ip_header *ip; 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 ip_len = lduw_be_p(&ip->ip_len); 111 112 /* Last, check that we have enough data for the all IP frame */ 113 if (length < ip_len) { 114 return; 115 } 116 117 ip_len -= IP_HDR_GET_LEN(ip); 118 119 switch (ip->ip_p) { 120 case IP_PROTO_TCP: 121 { 122 uint16_t csum; 123 tcp_header *tcp = (tcp_header *)(ip + 1); 124 125 if (ip_len < sizeof(tcp_header)) { 126 return; 127 } 128 129 /* Set csum to 0 */ 130 stw_he_p(&tcp->th_sum, 0); 131 132 csum = net_checksum_tcpudp(ip_len, ip->ip_p, 133 (uint8_t *)&ip->ip_src, 134 (uint8_t *)tcp); 135 136 /* Store computed csum */ 137 stw_be_p(&tcp->th_sum, csum); 138 139 break; 140 } 141 case IP_PROTO_UDP: 142 { 143 uint16_t csum; 144 udp_header *udp = (udp_header *)(ip + 1); 145 146 if (ip_len < sizeof(udp_header)) { 147 return; 148 } 149 150 /* Set csum to 0 */ 151 stw_he_p(&udp->uh_sum, 0); 152 153 csum = net_checksum_tcpudp(ip_len, ip->ip_p, 154 (uint8_t *)&ip->ip_src, 155 (uint8_t *)udp); 156 157 /* Store computed csum */ 158 stw_be_p(&udp->uh_sum, csum); 159 160 break; 161 } 162 default: 163 /* Can't handle any other protocol */ 164 break; 165 } 166 } 167 168 uint32_t 169 net_checksum_add_iov(const struct iovec *iov, const unsigned int iov_cnt, 170 uint32_t iov_off, uint32_t size, uint32_t csum_offset) 171 { 172 size_t iovec_off, buf_off; 173 unsigned int i; 174 uint32_t res = 0; 175 176 iovec_off = 0; 177 buf_off = 0; 178 for (i = 0; i < iov_cnt && size; i++) { 179 if (iov_off < (iovec_off + iov[i].iov_len)) { 180 size_t len = MIN((iovec_off + iov[i].iov_len) - iov_off , size); 181 void *chunk_buf = iov[i].iov_base + (iov_off - iovec_off); 182 183 res += net_checksum_add_cont(len, chunk_buf, csum_offset); 184 csum_offset += len; 185 186 buf_off += len; 187 iov_off += len; 188 size -= len; 189 } 190 iovec_off += iov[i].iov_len; 191 } 192 return res; 193 } 194