More work on IPv4 sockets and /bin/ping.

It's now actually possible to ping other hosts on the network! :^)
I've switched the "run" script over to starting QEMU with user networking
since that works better for my testing needs right now.

Userland/ping.cpp

@@ -4,23 +4,32 @@
 #include <stdio.h>
 #include <string.h>
 #include <unistd.h>
-#include <Kernel/NetworkOrdered.h>
+#include <time.h>
 
-NetworkOrdered<word> internet_checksum(const void* ptr, size_t count)
+uint16_t internet_checksum(const void* ptr, size_t count)
 {
-    dword checksum = 0;
-    auto* w = (const word*)ptr;
+    uint32_t  checksum = 0;
+    auto* w = (const uint16_t*)ptr;
     while (count > 1) {
-        checksum += convert_between_host_and_network(*w++);
+        checksum += ntohs(*w++);
         if (checksum & 0x80000000)
             checksum = (checksum & 0xffff) | (checksum >> 16);
         count -= 2;
     }
     while (checksum >> 16)
         checksum = (checksum & 0xffff) + (checksum >> 16);
-    return ~checksum & 0xffff;
+    return htons(~checksum);
 }
 
+inline void timersub(struct timeval* a, struct timeval* b, struct timeval* result)
+{
+    result->tv_sec = a->tv_sec - b->tv_sec;
+    result->tv_usec = a->tv_usec - b->tv_usec;
+    if (result->tv_usec < 0) {
+        --result->tv_sec;
+        result->tv_usec += 1000000;
+    }
+}
 
 int main(int argc, char** argv)
 {
@@ -30,42 +39,82 @@ int main(int argc, char** argv)
         return 1;
     }
 
+    const char* addr_str = "192.168.5.1";
+    if (argc > 1)
+        addr_str = argv[1];
+
+    pid_t pid = getpid();
+
     sockaddr_in peer_address;
     memset(&peer_address, 0, sizeof(peer_address));
     peer_address.sin_family = AF_INET;
     peer_address.sin_port = 0;
-    peer_address.sin_addr.s_addr = 0x0105a8c0; // 192.168.5.1
+
+    int rc = inet_pton(AF_INET, addr_str, &peer_address.sin_addr);
 
     struct PingPacket {
         struct icmphdr header;
         char msg[64 - sizeof(struct icmphdr)];
     };
 
-    PingPacket ping_packet;
-    PingPacket pong_packet;
-    memset(&ping_packet, 0, sizeof(PingPacket));
+    uint16_t seq = 1;
 
-    ping_packet.header.type = 8; // Echo request
-    ping_packet.header.code = 0;
-    ping_packet.header.un.echo.id = htons(getpid());
-    ping_packet.header.un.echo.sequence = htons(1);
-    strcpy(ping_packet.msg, "Hello there!\n");
+    for (;;) {
+        PingPacket ping_packet;
+        PingPacket pong_packet;
+        memset(&ping_packet, 0, sizeof(PingPacket));
 
-    ping_packet.header.checksum = htons(internet_checksum(&ping_packet, sizeof(PingPacket)));
+        ping_packet.header.type = 8; // Echo request
+        ping_packet.header.code = 0;
+        ping_packet.header.un.echo.id = htons(pid);
+        ping_packet.header.un.echo.sequence = htons(seq++);
+        strcpy(ping_packet.msg, "Hello there!\n");
 
-    int rc = sendto(fd, &ping_packet, sizeof(PingPacket), 0, (const struct sockaddr*)&peer_address, sizeof(sockaddr_in));
-    if (rc < 0) {
-        perror("sendto");
-        return 1;
+        ping_packet.header.checksum = internet_checksum(&ping_packet, sizeof(PingPacket));
+
+        struct timeval tv_send;
+        gettimeofday(&tv_send, nullptr);
+
+        rc = sendto(fd, &ping_packet, sizeof(PingPacket), 0, (const struct sockaddr*)&peer_address, sizeof(sockaddr_in));
+        if (rc < 0) {
+            perror("sendto");
+            return 1;
+        }
+
+        for (;;) {
+            rc = recvfrom(fd, &pong_packet, sizeof(PingPacket), 0, (const struct sockaddr*)&peer_address, sizeof(sockaddr_in));
+            if (rc < 0) {
+                perror("recvfrom");
+                return 1;
+            }
+
+            if (pong_packet.header.type != 0)
+                continue;
+            if (pong_packet.header.code != 0)
+                continue;
+            if (ntohs(pong_packet.header.un.echo.id) != pid)
+                continue;
+
+            struct timeval tv_receive;
+            gettimeofday(&tv_receive, nullptr);
+
+            struct timeval tv_diff;
+            timersub(&tv_receive, &tv_send, &tv_diff);
+
+            int ms = tv_diff.tv_sec * 1000 + tv_diff.tv_usec / 1000;
+
+            char addr_buf[64];
+            printf("Pong from %s: id=%u, seq=%u, time=%dms\n",
+                inet_ntop(AF_INET, &peer_address.sin_addr, addr_buf, sizeof(addr_buf)),
+                ntohs(pong_packet.header.un.echo.id),
+                ntohs(pong_packet.header.un.echo.sequence),
+                ms
+            );
+            break;
+        }
+
+        sleep(1);
     }
 
-    rc = recvfrom(fd, &pong_packet, sizeof(PingPacket), 0, (const struct sockaddr*)&peer_address, sizeof(sockaddr_in));
-    if (rc < 0) {
-        perror("recvfrom");
-        return 1;
-    }
-
-    printf("received %p (%d)\n", &pong_packet, rc);
-
     return 0;
 }