Added getnameinfo with only name lookup (#172)

Added necessary constants (DNS_TYPE_PTR, NI_NUMERICHOST etc.). Implementation of getnameinfo is similar to getaddrinfo, with internal functions: * ResolveDnsReverse: performs rDNS query and parses the PTR record * ResolveHostsReverse: reads /etc/hosts to map hostname to address Earlier, the HOSTS.txt would only need to be sorted at loading time, because the only kind of lookup was name -> address. Now since address -> name lookups are also possible, so the HostsTxt struct, the sorting method (and the related tests) was changed to reflect this.
2025-07-01 00:38:31 +00:00 · 2021-06-10 08:05:44 +05:30 · 2021-06-10 08:05:44 +05:30 · 248c6d54bb
commit 248c6d54bb
parent 05350eca60
12 changed files with 334 additions and 10 deletions
--- a/libc/dns/getnameinfo.c
+++ b/libc/dns/getnameinfo.c
@ -0,0 +1,107 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ This is free and unencumbered software released into the public domain.      │
+│                                                                              │
+│ Anyone is free to copy, modify, publish, use, compile, sell, or              │
+│ distribute this software, either in source code form or as a compiled        │
+│ binary, for any purpose, commercial or non-commercial, and by any            │
+│ means.                                                                       │
+│                                                                              │
+│ In jurisdictions that recognize copyright laws, the author or authors        │
+│ of this software dedicate any and all copyright interest in the              │
+│ software to the public domain. We make this dedication for the benefit       │
+│ of the public at large and to the detriment of our heirs and                 │
+│ successors. We intend this dedication to be an overt act of                  │
+│ relinquishment in perpetuity of all present and future rights to this        │
+│ software under copyright law.                                                │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,              │
+│ EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF           │
+│ MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.       │
+│ IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR            │
+│ OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,        │
+│ ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR        │
+│ OTHER DEALINGS IN THE SOFTWARE.                                              │
+│                                                                              │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/bits/safemacros.internal.h"
+#include "libc/calls/calls.h"
+#include "libc/dns/consts.h"
+#include "libc/dns/dns.h"
+#include "libc/dns/hoststxt.h"
+#include "libc/dns/resolvconf.h"
+#include "libc/fmt/conv.h"
+#include "libc/fmt/fmt.h"
+#include "libc/mem/mem.h"
+#include "libc/sock/sock.h"
+#include "libc/str/str.h"
+#include "libc/sysv/consts/af.h"
+#include "libc/sysv/consts/inaddr.h"
+#include "libc/sysv/errfuns.h"
+
+/**
+ * Resolves name/service for socket address.
+ *
+ * @param addr
+ * @param addrlen
+ * @param name
+ * @param namelen
+ * @param service
+ * @param servicelen
+ * @param flags
+ *
+ * @return 0 on success or EAI_xxx value
+ */
+int getnameinfo(const struct sockaddr *addr, socklen_t addrlen, char *name,
+                socklen_t namelen, char *service, socklen_t servicelen,
+                int flags) {
+  char rdomain[1 + sizeof "255.255.255.255.in-addr.arpa"];
+  char info[512];
+  int rc, port;
+  uint8_t *ip;
+  unsigned int valid_flags;
+
+  valid_flags =
+      (NI_NAMEREQD | NI_NUMERICHOST | NI_NUMERICSERV | NI_NOFQDN | NI_DGRAM);
+
+  if (flags & ~(valid_flags)) return EAI_BADFLAGS;
+  if (!name && !service) return EAI_NONAME;
+  if (addr->sa_family != AF_INET || addrlen < sizeof(struct sockaddr_in))
+    return EAI_FAMILY;
+
+  ip = (uint8_t *)&(((struct sockaddr_in *)addr)->sin_addr);
+  sprintf(rdomain, "%d.%d.%d.%d.in-addr.arpa", ip[3], ip[2], ip[1], ip[0]);
+  info[0] = '\0';
+  if (name != NULL && namelen != 0) {
+    if ((flags & NI_NUMERICHOST) && (flags & NI_NAMEREQD)) return EAI_NONAME;
+
+    if ((flags & NI_NUMERICHOST) &&
+        inet_ntop(AF_INET, ip, info, sizeof(info)) == NULL)
+      return EAI_SYSTEM;
+    else if (!info[0] && ResolveHostsReverse(GetHostsTxt(), AF_INET, ip, info,
+                                             sizeof(info)) < 0)
+      return EAI_SYSTEM;
+    else if (!info[0] && ResolveDnsReverse(GetResolvConf(), AF_INET, rdomain,
+                                           info, sizeof(info)) < 0)
+      return EAI_SYSTEM;
+    else if (!info[0] && (flags & NI_NAMEREQD))
+      return EAI_NONAME;
+    else if (!info[0] && inet_ntop(AF_INET, ip, info, sizeof(info)) == NULL)
+      return EAI_SYSTEM;
+
+    if (strlen(info) + 1 > namelen) return EAI_OVERFLOW;
+    strcpy(name, info);
+  }
+
+  port = ntohs(((struct sockaddr_in *)addr)->sin_port);
+  info[0] = '\0';
+  if (service != NULL && servicelen != 0) {
+    itoa(port, info, 10);
+    /* TODO: reverse lookup on /etc/services to get name of service */
+    if (strlen(info) + 1 > servicelen) return EAI_OVERFLOW;
+    strcpy(service, info);
+  }
+
+  return 0;
+}