github.com/datadog/cilium@v1.6.12/bpf/lib/csum.h (about) 1 /* 2 * Copyright (C) 2016-2017 Authors of Cilium 3 * 4 * This program is free software; you can redistribute it and/or modify 5 * it under the terms of the GNU General Public License as published by 6 * the Free Software Foundation; either version 2 of the License, or 7 * (at your option) any later version. 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, write to the Free Software 16 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA 17 */ 18 19 #ifndef __LIB_CSUM_H_ 20 #define __LIB_CSUM_H_ 21 22 #include <linux/tcp.h> 23 #include <linux/udp.h> 24 #include <linux/icmpv6.h> 25 26 #define TCP_CSUM_OFF (offsetof(struct tcphdr, check)) 27 #define UDP_CSUM_OFF (offsetof(struct udphdr, check)) 28 29 struct csum_offset 30 { 31 __u16 offset; 32 __u16 flags; 33 }; 34 35 /** 36 * Determins the L4 checksum field offset and required flags 37 * @arg nexthdr L3 nextheader field 38 * @arg off Pointer to uninitialied struct csum_offset struct 39 * 40 * Sets off.offset to offset from start of L4 header to L4 checksum field 41 * and off.flags to the required flags, namely BPF_F_MARK_MANGLED_0 for UDP. 42 * For unknown L4 protocols or L4 protocols which do not have a checksum 43 * field, off is initialied to 0. 44 */ 45 static inline void csum_l4_offset_and_flags(__u8 nexthdr, struct csum_offset *off) 46 { 47 switch (nexthdr) { 48 case IPPROTO_TCP: 49 off->offset = TCP_CSUM_OFF; 50 break; 51 52 case IPPROTO_UDP: 53 off->offset = UDP_CSUM_OFF; 54 off->flags = BPF_F_MARK_MANGLED_0; 55 break; 56 57 case IPPROTO_ICMPV6: 58 off->offset = offsetof(struct icmp6hdr, icmp6_cksum); 59 break; 60 61 case IPPROTO_ICMP: 62 break; 63 } 64 } 65 66 /** 67 * Helper to change L4 checksum 68 * @arg skb Packet 69 * @arg l4_off Offset to L4 header 70 * @arg csum Pointer to csum_offset as extracted by csum_l4_offset_and_flags() 71 * @arg from From value or 0 if to contains csum diff 72 * @arg to To value or a csum diff 73 * @arg flags Additional flags to be passed to l4_csum_replace() 74 */ 75 static inline int csum_l4_replace(struct __sk_buff *skb, int l4_off, struct csum_offset *csum, 76 __be32 from, __be32 to, int flags) 77 { 78 return l4_csum_replace(skb, l4_off + csum->offset, from, to, flags | csum->flags); 79 } 80 81 #endif /* __LB_H_ */