net: ping resolves hostnames (ping sl0p.foo, not just ping 1.2.3.4)

ping used parse_ip only, so a hostname gave "bad address". It now uses resolve.h
(like wget/nslookup): dotted-quad is used as-is, a name is looked up via DNS
first. Copies the arg to a safe buffer before resolving (the 0xA000 arg/_DATA
overlap dance).

Verified through DHCP + NAT:
    /# ping sl0p.foo
    PING 80.78.19.56
      reply from 80.78.19.56 seq=1 ... -- 4/4 received

1 files changed, 15 insertions, 21 deletions

diff --git a/c/ping.c b/c/ping.c
index 68c4c86..f8d5bf7 100644
--- a/c/ping.c
+++ b/c/ping.c
@@ -1,26 +1,14 @@
-#include "sock.h"
-/* ping - originate ICMP echo requests via the kernel socket layer. No SLIP,
-   no IP, no checksums here: the kernel owns all of that. Usage: ping [A.B.C.D]
-   (default 10.0.0.1, the SLIP peer/host; reaches real hosts through NAT). */
+#include "resolve.h"
+/* ping HOST|IP - originate ICMP echo requests via the kernel socket layer.
+   Resolves a hostname via DNS first (resolve.h); default target 10.0.0.1. No
+   SLIP/IP/checksums here - the kernel owns all of that. */
 
-/* rbuf is declared first (and large) so the parse target dst[] lands well past
-   the argument string the shell leaves at 0xA000 - writing dst must not clobber
-   the arg while we're still reading it. */
+/* rbuf is first + large so namebuf/dst land past the arg string at 0xA000 */
 static unsigned char rbuf[96];
+static unsigned char namebuf[64];
 static unsigned char dst[4];
 static unsigned char payload[4];
 
-static unsigned char parse_ip(char *s, unsigned char *out) {
-    unsigned char i, v;
-    for (i = 0; i < 4; i++) {
-        if (*s < '0' || *s > '9') return 0;
-        v = 0;
-        while (*s >= '0' && *s <= '9') { v = (unsigned char)(v * 10 + (*s - '0')); s++; }
-        out[i] = v;
-        if (i < 3) { if (*s != '.') return 0; s++; }
-    }
-    return 1;
-}
 static void put_ip(unsigned char *ip) {
     unsigned char i;
     for (i = 0; i < 4; i++) { putu(ip[i]); if (i < 3) putc('.'); }
@@ -28,10 +16,16 @@ static void put_ip(unsigned char *ip) {
 
 void main(void) {
     char *arg;
-    unsigned char s, seq, got = 0;
+    unsigned char s, seq, got = 0, i;
     arg = getargs();
     if (!arg || !*arg) { dst[0] = 10; dst[1] = 0; dst[2] = 0; dst[3] = 1; }
-    else if (!parse_ip(arg, dst)) { puts("ping: bad address"); nl(); sexit(1); }
+    else {
+        for (i = 0; arg[i] && i < 63; i++) namebuf[i] = (unsigned char)arg[i];
+        namebuf[i] = 0;
+        if (!resolve((char *)namebuf, dst)) {
+            puts("ping: cannot resolve "); puts((char *)namebuf); nl(); sexit(1);
+        }
+    }
 
     payload[0] = 'g'; payload[1] = 'b'; payload[2] = 'o'; payload[3] = 's';
     s = net_socket(SOCK_ICMP);
@@ -41,7 +35,7 @@ void main(void) {
     puts("PING "); put_ip(dst); nl();
     for (seq = 1; seq <= 4; seq++) {
         net_send(s, payload, 4);
-        if (net_recv(s, rbuf, sizeof(rbuf)) != 0xFF) {
+        if (net_recv(s, rbuf, (unsigned char)sizeof(rbuf)) != 0xFF) {
             got++;
             puts("  reply from "); put_ip(dst); puts(" seq="); putu(seq); nl();
         } else {