1 files changed, 156 insertions, 0 deletions
diff --git a/src/inet.c b/src/inet.c
new file mode 100644
index 0000000..5f7fb7d
--- /dev/null
+++ b/src/inet.c
@@ -0,0 +1,156 @@
+#include "inet.h"
+#include "endian.h"
+
+
+void prne_netmask_from_cidr (uint8_t *out, size_t cidr) {
+	size_t shft = 7;
+
+	while (cidr >= 8) {
+		*out = 0xFF;
+		cidr -= 8;
+		out += 1;
+	}
+	*out = 0;
+	while (cidr > 0) {
+		*out |= (uint8_t)(1 << shft);
+		shft -= 1;
+		cidr -= 1;
+	}
+}
+
+uint16_t prne_calc_tcp_chksum4 (
+	const struct iphdr *ih,
+	const uint8_t *th,
+	size_t th_len,
+	const uint8_t *data,
+	size_t data_len)
+{
+	uint_fast32_t sum = 0;
+
+	// pseudo
+	sum += prne_recmb_msb16(
+		((uint8_t*)&ih->saddr)[0],
+		((uint8_t*)&ih->saddr)[1]);
+	sum += prne_recmb_msb16(
+		((uint8_t*)&ih->saddr)[2],
+		((uint8_t*)&ih->saddr)[3]);
+
+	sum += prne_recmb_msb16(
+		((uint8_t*)&ih->daddr)[0],
+		((uint8_t*)&ih->daddr)[1]);
+	sum += prne_recmb_msb16(
+		((uint8_t*)&ih->daddr)[2],
+		((uint8_t*)&ih->daddr)[3]);
+	sum += 6; // IPPROTO_TCP
+	sum += (uint16_t)(th_len + data_len);
+
+	// tcp header
+	while (th_len > 1) {
+		sum += prne_recmb_msb16(th[0], th[1]);
+		th += 2;
+		th_len -= 2;
+	}
+	if (th_len > 0) {
+		sum += th[0];
+	}
+
+	// data
+	while (data_len > 1) {
+		sum += prne_recmb_msb16(data[0], data[1]);
+		data += 2;
+		data_len -= 2;
+	}
+	if (data_len > 0) {
+		sum += data[0];
+	}
+
+	return ~((sum & 0xFFFF) + (sum >> 16));
+}
+
+uint16_t prne_calc_tcp_chksum6 (
+	const struct ipv6hdr *ih,
+	const uint8_t *th,
+	size_t th_len,
+	const uint8_t *data,
+	size_t data_len)
+{
+	uint_fast32_t sum = 0;
+	const uint_fast32_t tcp_length = (uint32_t)(th_len + data_len);
+
+	// pseudo
+	sum += prne_recmb_msb16(
+		((const uint8_t*)&ih->saddr)[0],
+		((const uint8_t*)&ih->saddr)[1]);
+	sum += prne_recmb_msb16(
+		((const uint8_t*)&ih->saddr)[2],
+		((const uint8_t*)&ih->saddr)[3]);
+	sum += prne_recmb_msb16(
+		((const uint8_t*)&ih->saddr)[4],
+		((const uint8_t*)&ih->saddr)[5]);
+	sum += prne_recmb_msb16(
+		((const uint8_t*)&ih->saddr)[6],
+		((const uint8_t*)&ih->saddr)[7]);
+	sum += prne_recmb_msb16(
+		((const uint8_t*)&ih->saddr)[8],
+		((const uint8_t*)&ih->saddr)[9]);
+	sum += prne_recmb_msb16(
+		((const uint8_t*)&ih->saddr)[10],
+		((const uint8_t*)&ih->saddr)[11]);
+	sum += prne_recmb_msb16(
+		((const uint8_t*)&ih->saddr)[12],
+		((const uint8_t*)&ih->saddr)[13]);
+	sum += prne_recmb_msb16(
+		((const uint8_t*)&ih->saddr)[14],
+		((const uint8_t*)&ih->saddr)[15]);
+
+	sum += prne_recmb_msb16(
+		((const uint8_t*)&ih->daddr)[0],
+		((const uint8_t*)&ih->daddr)[1]);
+	sum += prne_recmb_msb16(
+		((const uint8_t*)&ih->daddr)[2],
+		((const uint8_t*)&ih->daddr)[3]);
+	sum += prne_recmb_msb16(
+		((const uint8_t*)&ih->daddr)[4],
+		((const uint8_t*)&ih->daddr)[5]);
+	sum += prne_recmb_msb16(
+		((const uint8_t*)&ih->daddr)[6],
+		((const uint8_t*)&ih->daddr)[7]);
+	sum += prne_recmb_msb16(
+		((const uint8_t*)&ih->daddr)[8],
+		((const uint8_t*)&ih->daddr)[9]);
+	sum += prne_recmb_msb16(
+		((const uint8_t*)&ih->daddr)[10],
+		((const uint8_t*)&ih->daddr)[11]);
+	sum += prne_recmb_msb16(
+		((const uint8_t*)&ih->daddr)[12],
+		((const uint8_t*)&ih->daddr)[13]);
+	sum += prne_recmb_msb16(
+		((const uint8_t*)&ih->daddr)[14],
+		((const uint8_t*)&ih->daddr)[15]);
+
+	sum += (uint16_t)((tcp_length & 0xFFFF0000) >> 16);
+	sum += (uint16_t)(tcp_length & 0xFFFF);
+	sum += 6; // IPPROTO_TCP
+
+	// tcp header
+	while (th_len > 1) {
+		sum += prne_recmb_msb16(th[0], th[1]);
+		th += 2;
+		th_len -= 2;
+	}
+	if (th_len > 0) {
+		sum += th[0];
+	}
+
+	// data
+	while (data_len > 1) {
+		sum += prne_recmb_msb16(data[0], data[1]);
+		data += 2;
+		data_len -= 2;
+	}
+	if (data_len > 0) {
+		sum += data[0];
+	}
+
+	return ~((sum & 0xFFFF) + (sum >> 16));
+}