apf: add apf_{defs,utils,checksum,dns}.h helper/header files
Test: in following CLs
Signed-off-by: Maciej Żenczykowski <[email protected]>
Co-developed-by: Yuyang Huang <[email protected]>
Change-Id: Idc44049848bf83a6b13cf45b57ff89a6f3057683
diff --git a/apf_checksum.h b/apf_checksum.h
new file mode 100644
index 0000000..acfd36c
--- /dev/null
+++ b/apf_checksum.h
@@ -0,0 +1,80 @@
+/**
+ * Calculate big endian 16-bit sum of a buffer (max 128kB),
+ * then fold and negate it, producing a 16-bit result in [0..FFFE].
+ */
+u16 calc_csum(u32 sum, const u8* const buf, const u32 len) {
+ u32 i;
+ for (i = 0; i < len; ++i) sum += buf[i] * ((i & 1) ? 1 : 256);
+
+ sum = (sum & 0xFFFF) + (sum >> 16); /* max after this is 1FFFE */
+ u16 csum = sum + (sum >> 16);
+ return ~csum; /* assuming sum > 0 on input, this is in [0..FFFE] */
+}
+
+static u16 fix_udp_csum(u16 csum) {
+ return csum ? csum : 0xFFFF;
+}
+
+/**
+ * Calculate the ipv4 header and tcp/udp layer 4 checksums.
+ * (assumes IPv4 checksum field is set to partial sum of ipv4 options [likely 0])
+ * (assumes L4 checksum field is set to L4 payload length on input)
+ * Warning: TCP/UDP L4 checksum corrupts packet iff ipv4 options are present.
+ * Returns 6-bit DSCP value [0..63], -1 on parse error.
+ */
+static int calc_ipv4_csum(u8* const ip4_pkt, const u32 len) {
+ if (len < IPV4_HLEN) return -1;
+ store_be16(ip4_pkt + 10, calc_csum(0xFFFF, ip4_pkt, IPV4_HLEN));
+
+ u8 proto = ip4_pkt[9];
+ u16 csum = calc_csum(proto, ip4_pkt + 12, len - 12);
+ switch (proto) {
+ case IPPROTO_TCP:
+ if (len >= IPV4_HLEN + TCP_HLEN) store_be16(ip4_pkt + IPV4_HLEN + 16, csum);
+ break;
+ case IPPROTO_UDP:
+ if (len >= IPV4_HLEN + UDP_HLEN) store_be16(ip4_pkt + IPV4_HLEN + 6, fix_udp_csum(csum));
+ break;
+ }
+ return ip4_pkt[1] >> 2; /* DSCP */
+}
+
+/**
+ * Calculate the ipv6 icmp6/tcp/udp layer 4 checksums.
+ * (assumes L4 checksum field is set to L4 payload length on input)
+ * Returns 6-bit DSCP value [0..63], -1 on parse error.
+ */
+static int calc_ipv6_csum(u8* const ip6_pkt, const u32 len) {
+ if (len < IPV6_HLEN) return -1;
+ u8 proto = ip6_pkt[6];
+ u16 csum = calc_csum(proto, ip6_pkt + 8, len - 8);
+ switch (proto) {
+ case IPPROTO_ICMPV6:
+ if (len >= IPV6_HLEN + 4) store_be16(ip6_pkt + IPV6_HLEN + 2, csum);
+ break;
+ case IPPROTO_TCP:
+ if (len >= IPV6_HLEN + TCP_HLEN) store_be16(ip6_pkt + IPV6_HLEN + 16, csum);
+ break;
+ case IPPROTO_UDP:
+ if (len >= IPV6_HLEN + UDP_HLEN) store_be16(ip6_pkt + IPV6_HLEN + 6, fix_udp_csum(csum));
+ break;
+ }
+ return (read_be16(ip6_pkt) >> 6) & 0x3F; /* DSCP */
+}
+
+/**
+ * Calculate and store packet checksums and return dscp.
+ *
+ * @param pkt - pointer to the start of the ethernet header of the packet.
+ * @param len - length of the packet.
+ *
+ * @return 6-bit DSCP value [0..63] or -1 on parse error.
+ */
+int calculate_checksum_and_return_dscp(u8* const pkt, const u32 len) {
+ if (len < ETH_HLEN) return -1;
+ switch (read_be16(pkt + 12)) { /* ethertype */
+ case ETH_P_IP: return calc_ipv4_csum(pkt + ETH_HLEN, len - ETH_HLEN);
+ case ETH_P_IPV6: return calc_ipv6_csum(pkt + ETH_HLEN, len - ETH_HLEN);
+ default: return 0;
+ }
+}
