From 86799647b1afbaa0df36718b216efd876ffd2627 Mon Sep 17 00:00:00 2001
From: "Alex Xu (Hello71)" <alex_y_xu@yahoo.ca>
Date: Sat, 2 Jul 2016 19:47:51 -0400
Subject: Add start of checksumming.

---
 src/checksum.h | 27 ++++++++++++++++++++++++
 src/client.c   | 66 ++++++++++++++++++++++++++++++++++++++++------------------
 2 files changed, 73 insertions(+), 20 deletions(-)
 create mode 100644 src/checksum.h

diff --git a/src/checksum.h b/src/checksum.h
new file mode 100644
index 0000000..d9e6bda
--- /dev/null
+++ b/src/checksum.h
@@ -0,0 +1,27 @@
+#include <stdint.h>
+
+static inline uint16_t do_csum(const char *buf, unsigned size) {
+    unsigned int sum = 0;
+    unsigned int i;
+
+    for (i = 0; i < size - 1; i += 2)
+        sum += *(uint16_t *)&buf[i];
+
+    if (size & 1)
+        sum += (uint8_t)buf[i];
+
+    while (sum >> 16)
+        sum = (sum & 0xFFFF) + (sum >> 16);
+
+    return ~sum;
+}
+
+static inline uint16_t csum_partial(const void *buff, int len, uint16_t wsum) {
+    unsigned int sum = (unsigned int)wsum;
+    unsigned int result = do_csum(buff, len);
+
+    result += sum;
+    if (sum > result)
+        result += 1;
+    return result;
+}
diff --git a/src/client.c b/src/client.c
index 80943fb..71edf3e 100644
--- a/src/client.c
+++ b/src/client.c
@@ -11,6 +11,7 @@
 #include <unistd.h>
 
 #include "common.h"
+#include "checksum.h"
 #include "client.h"
 #include "uthash.h"
 
@@ -20,11 +21,12 @@ struct o_c_rsock {
     struct sockaddr *r_addr;
     struct o_c_sock *o_socks_by_lport;
     struct c_data *c_data;
+    unsigned int used_ports[32768 / PORTS_IN_INT];
     ev_io io_w;
     UT_hash_handle hh;
     int fd;
+    uint16_t csum_a;
     socklen_t r_addrlen;
-    unsigned int used_ports[32768 / PORTS_IN_INT];
 };
 
 struct o_c_sock {
@@ -281,6 +283,47 @@ static void cc_cb(struct ev_loop *loop, ev_io *w, int revents __attribute__((unu
     }
 }
 
+#define SIX_OR_FOUR(sa, six, four, neither) \
+    (((struct sockaddr *)(sa))->sa_family == AF_INET6 ? (six) : ((struct sockaddr *)(sa))->sa_family == AF_INET ? (four) : abort(), neither)
+
+#define EXTRACT_IN_ADDR(sa) \
+    SIX_OR_FOUR((struct sockaddr *)(sa), &(((struct sockaddr_in6 *)(sa))->sin6_addr), &(((struct sockaddr_in *)(sa))->sin_addr), NULL), \
+    SIX_OR_FOUR((struct sockaddr *)(sa), sizeof(struct in6_addr), sizeof(in_addr_t), 0)
+
+static int c_rsock_init(struct o_c_sock *sock, struct addrinfo *res) {
+    sock->rsock = malloc(sizeof(*sock->rsock));
+    memset(&sock->rsock->used_ports, 0, sizeof(sock->rsock->used_ports));
+    sock->rsock->r_addr = malloc(res->ai_addrlen);
+
+    memcpy(sock->rsock->r_addr, res->ai_addr, res->ai_addrlen);
+    sock->rsock->r_addrlen = res->ai_addrlen;
+    freeaddrinfo(res);
+    sock->rsock->o_socks_by_lport = NULL;
+
+    sock->rsock->fd = socket(sock->rsock->r_addr->sa_family, SOCK_RAW, IPPROTO_TCP);
+    if (!sock->rsock->fd) {
+        perror("socket");
+        return 0;
+    }
+
+    if (connect(sock->rsock->fd, sock->rsock->r_addr, sock->rsock->r_addrlen) == -1) {
+        perror("connect");
+        return 0;
+    }
+
+    struct sockaddr_storage our_addr;
+    socklen_t our_addr_len = sizeof(our_addr);
+    int r = getsockname(sock->rsock->fd, (struct sockaddr *)&our_addr, &our_addr_len);
+    if (r == -1) {
+        perror("getsockname");
+        return 0;
+    }
+
+    //sock->rsock->csum_a = csum_partial(EXTRACT_IN_ADDR(sock->rsock->r_addr), csum_partial(EXTRACT_IN_ADDR(&our_addr), 0));
+
+    return 1;
+}
+
 static void cs_cb(EV_P_ ev_io *w, int revents __attribute__((unused))) {
     DBG("-- entering cs_cb --");
     struct c_data *c_data = w->data;
@@ -323,28 +366,11 @@ static void cs_cb(EV_P_ ev_io *w, int revents __attribute__((unused))) {
 
         if (!sock->rsock) {
             DBG("could not locate remote socket to host, initializing new raw socket");
-            sock->rsock = malloc(sizeof(*sock->rsock));
-            memset(&sock->rsock->used_ports, 0, sizeof(sock->rsock->used_ports));
-            sock->rsock->r_addr = malloc(res->ai_addrlen);
-
-            memcpy(sock->rsock->r_addr, res->ai_addr, res->ai_addrlen);
-            sock->rsock->r_addrlen = res->ai_addrlen;
-            freeaddrinfo(res);
-            sock->rsock->o_socks_by_lport = NULL;
-            sock->rsock->c_data = c_data;
-
-            sock->rsock->fd = socket(sock->rsock->r_addr->sa_family, SOCK_RAW, IPPROTO_TCP);
-            if (!sock->rsock->fd) {
-                perror("socket");
-                ev_break(EV_A_ EVBREAK_ONE);
-                return;
-            }
-
-            if (connect(sock->rsock->fd, sock->rsock->r_addr, sock->rsock->r_addrlen) == -1) {
-                perror("connect");
+            if (!c_rsock_init(sock, res)) {
                 ev_break(EV_A_ EVBREAK_ONE);
                 return;
             }
+            sock->rsock->c_data = c_data;
 
             ev_io_init(&sock->rsock->io_w, cc_cb, sock->rsock->fd, EV_READ);
             sock->rsock->io_w.data = sock->rsock;
-- 
cgit v1.2.3-54-g00ecf