Initial commit.

.editorconfig

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+root = true
+
+[*]
+indent_size = 2
+indent_style = space
+end_of_line = lf
+insert_final_newline = true
+
+[Makefile]
+indent_style = tab

Dockerfile

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+FROM postgres:14
+
+RUN apt-get update
+RUN apt-get install -y build-essential
+RUN apt-get install -y postgresql-server-dev-14
+COPY rdns.c Makefile rdns.control rdns--1.0.sql /usr/src/rdns/
+RUN cd /usr/src/rdns/; \
+  make; \
+  make install; \
+  echo "shared_preload_libraries = 'rdns'" >> $PGDATA/postgresql.conf;

Makefile

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+OBJS = rdns.o
+
+EXTENSION = rdns
+DATA = rdns--1.0.sql
+MODULES = rdns
+
+PG_CONFIG = pg_config
+PGXS := $(shell $(PG_CONFIG) --pgxs)
+include $(PGXS)

docker-compose.yml

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+services:
+  postgres:
+    build: .
+    image: registry.xnopyt.com/postgres-rdns:14

rdns--1.0.sql

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+CREATE FUNCTION rdns_lookup(text)
+RETURNS text
+AS '$libdir/rdns'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION circular_rdns_lookup(text)
+RETURNS text
+AS '$libdir/rdns'
+LANGUAGE C STRICT;

rdns.c

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+#include "postgres.h"
+#include "fmgr.h"
+#include "utils/builtins.h"
+#include <arpa/inet.h>
+#include <sys/socket.h>
+#include <netdb.h>
+#include <sys/types.h>
+
+PG_MODULE_MAGIC;
+
+
+PG_FUNCTION_INFO_V1(rdns_lookup);
+Datum rdns_lookup(PG_FUNCTION_ARGS) {
+  struct in_addr iaddr;
+  char host[512];
+  struct sockaddr_in sa;
+  int r;
+  char* ip = text_to_cstring(PG_GETARG_TEXT_PP(0));
+
+  memset(&iaddr, 0, sizeof(struct in_addr));
+  memset(&sa, 0, sizeof(struct sockaddr_in));
+  memset(host, 0, 512);
+
+  inet_aton(ip, &iaddr);
+
+  sa.sin_family = AF_INET;
+  sa.sin_addr = iaddr;
+
+  r = getnameinfo((struct sockaddr*)(&sa), sizeof(struct sockaddr_in), host, 512, 0, 0, NI_NAMEREQD);
+  if (r == EAI_NONAME)
+    PG_RETURN_NULL();
+  if (r) {
+    ereport(ERROR, (errcode(ERRCODE_SYSTEM_ERROR), errmsg("getnameinfo failed! %s", gai_strerror(r))));
+  }
+
+  PG_RETURN_TEXT_P(cstring_to_text(host));
+}
+
+PG_FUNCTION_INFO_V1(circular_rdns_lookup);
+Datum circular_rdns_lookup(PG_FUNCTION_ARGS) {
+  struct in_addr iaddr;
+  char host[512];
+  struct sockaddr_in sa;
+  int r;
+  struct addrinfo hint;
+  struct addrinfo* results;
+  char* ip = text_to_cstring(PG_GETARG_TEXT_PP(0));
+  struct addrinfo* c;
+
+  memset(&iaddr, 0, sizeof(struct in_addr));
+  memset(&sa, 0, sizeof(struct sockaddr_in));
+  memset(host, 0, 512);
+  memset(&hint, 0, sizeof(struct addrinfo));
+
+  inet_aton(ip, &iaddr);
+
+  sa.sin_family = AF_INET;
+  sa.sin_addr = iaddr;
+
+  r = getnameinfo((struct sockaddr*)(&sa), sizeof(struct sockaddr_in), host, 512, 0, 0, NI_NAMEREQD);
+  if (r == EAI_NONAME)
+    PG_RETURN_NULL();
+  if (r) {
+    ereport(ERROR, (errcode(ERRCODE_SYSTEM_ERROR), errmsg("getnameinfo failed! %s", gai_strerror(r))));
+  }
+
+  hint.ai_family = AF_INET;
+
+  r = getaddrinfo(host, 0, &hint, &results);
+  if (r) {
+    ereport(ERROR, (errcode(ERRCODE_SYSTEM_ERROR), errmsg("getaddrinfo failed! %s", gai_strerror(r))));
+  }
+
+  c = results;
+  while (c) {
+    struct addrinfo* current = c;
+    c = current->ai_next;
+    if (current->ai_family != AF_INET)
+      continue;
+
+    if (((struct sockaddr_in*)current->ai_addr)->sin_addr.s_addr == iaddr.s_addr) {
+      freeaddrinfo(results);
+      PG_RETURN_TEXT_P(cstring_to_text(host));
+    }
+  }
+
+  freeaddrinfo(results);
+  PG_RETURN_NULL();
+}

rdns.control

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+comment = 'Reverse DNS Extension for PostgreSQL'
+default_version = '1.0'
+relocatable = true