Adding an address parameter that allows nghttpd to bind to a non-default address. Both IPv4 and IPv6 addresses are supported. In addition with verbose mode enable the address that the webserver binds to is now printed in addition to the port.

src/HttpServer.cc

@@ -31,6 +31,7 @@
 #include <fcntl.h>
 #include <netinet/in.h>
 #include <netinet/tcp.h>
+#include <arpa/inet.h>
 
 #include <cassert>
 #include <set>
@@ -1459,12 +1460,34 @@ int verify_callback(int preverify_ok, X509_STORE_CTX *ctx) {
 }
 } // namespace
 
+namespace {
+// finds a readable address and adds stores it in the given string
+char *get_ip_str(const struct sockaddr *sa, char *s, size_t maxlen) {
+  switch (sa->sa_family) {
+  case AF_INET:
+    inet_ntop(AF_INET, &(((struct sockaddr_in *)sa)->sin_addr), s, maxlen);
+    break;
+
+  case AF_INET6:
+    inet_ntop(AF_INET6, &(((struct sockaddr_in6 *)sa)->sin6_addr), s, maxlen);
+    break;
+
+  default:
+    strncpy(s, "Unknown AF", maxlen);
+    return NULL;
+  }
+
+  return s;
+}
+} // namespace
+
 namespace {
 int start_listen(struct ev_loop *loop, Sessions *sessions,
                  const Config *config) {
   addrinfo hints;
   int r;
   bool ok = false;
+  const char *addr = nullptr;
 
   auto acceptor = std::make_shared<AcceptHandler>(sessions, config);
   auto service = util::utos(config->port);
@@ -1477,12 +1500,17 @@ int start_listen(struct ev_loop *loop, Sessions *sessions,
   hints.ai_flags |= AI_ADDRCONFIG;
 #endif // AI_ADDRCONFIG
 
+  if (!config->address.empty()) {
+    addr = config->address.c_str();
+  }
+
   addrinfo *res, *rp;
-  r = getaddrinfo(nullptr, service.c_str(), &hints, &res);
+  r = getaddrinfo(addr, service.c_str(), &hints, &res);
   if (r != 0) {
     std::cerr << "getaddrinfo() failed: " << gai_strerror(r) << std::endl;
     return -1;
   }
+
   for (rp = res; rp; rp = rp->ai_next) {
     int fd = socket(rp->ai_family, rp->ai_socktype, rp->ai_protocol);
     if (fd == -1) {
@@ -1508,8 +1536,10 @@ int start_listen(struct ev_loop *loop, Sessions *sessions,
       new ListenEventHandler(sessions, fd, acceptor);
 
       if (config->verbose) {
-        std::cout << (rp->ai_family == AF_INET ? "IPv4" : "IPv6")
+        char s[INET6_ADDRSTRLEN];
-                  << ": listen on port " << config->port << std::endl;
+        get_ip_str((struct sockaddr *)rp->ai_addr, s, sizeof s);
+        std::cout << (rp->ai_family == AF_INET ? "IPv4" : "IPv6") << ": listen "
+                  << s << ":" << config->port << std::endl;
       }
       ok = true;
       continue;

src/HttpServer.h

@@ -55,6 +55,7 @@ struct Config {
   std::string private_key_file;
   std::string cert_file;
   std::string dh_param_file;
+  std::string address;
   ev_tstamp stream_read_timeout;
   ev_tstamp stream_write_timeout;
   nghttp2_option *session_option;

src/nghttpd.cc

@@ -97,6 +97,9 @@ void print_help(std::ostream &out) {
   <CERT>      Set  path  to  server's  certificate.   Required  unless
               --no-tls is specified.
 Options:
+  -a  --address
+              The address to bind to.  If not specified the default IP
+              address determined by getaddrinfo is used.
   -D, --daemon
               Run in a background.  If -D is used, the current working
               directory is  changed to '/'.  Therefore  if this option
@@ -151,30 +154,35 @@ int main(int argc, char **argv) {
   while (1) {
     static int flag = 0;
     static option long_options[] = {
-        {"daemon", no_argument, nullptr, 'D'},
+      { "address", required_argument, nullptr, 'a' },
-        {"htdocs", required_argument, nullptr, 'd'},
+      { "daemon", no_argument, nullptr, 'D' },
-        {"help", no_argument, nullptr, 'h'},
+      { "htdocs", required_argument, nullptr, 'd' },
-        {"verbose", no_argument, nullptr, 'v'},
+      { "help", no_argument, nullptr, 'h' },
-        {"verify-client", no_argument, nullptr, 'V'},
+      { "verbose", no_argument, nullptr, 'v' },
-        {"header-table-size", required_argument, nullptr, 'c'},
+      { "verify-client", no_argument, nullptr, 'V' },
-        {"push", required_argument, nullptr, 'p'},
+      { "header-table-size", required_argument, nullptr, 'c' },
-        {"padding", required_argument, nullptr, 'b'},
+      { "push", required_argument, nullptr, 'p' },
-        {"workers", required_argument, nullptr, 'n'},
+      { "padding", required_argument, nullptr, 'b' },
-        {"error-gzip", no_argument, nullptr, 'e'},
+      { "workers", required_argument, nullptr, 'n' },
-        {"no-tls", no_argument, &flag, 1},
+      { "error-gzip", no_argument, nullptr, 'e' },
-        {"color", no_argument, &flag, 2},
+      { "no-tls", no_argument, &flag, 1 },
-        {"version", no_argument, &flag, 3},
+      { "color", no_argument, &flag, 2 },
-        {"dh-param-file", required_argument, &flag, 4},
+      { "version", no_argument, &flag, 3 },
-        {"early-response", no_argument, &flag, 5},
+      { "dh-param-file", required_argument, &flag, 4 },
-        {nullptr, 0, nullptr, 0}};
+      { "early-response", no_argument, &flag, 5 },
+      { nullptr, 0, nullptr, 0 }
+    };
     int option_index = 0;
-    int c =
+    int c = getopt_long(argc, argv, "DVb:c:d:ehn:p:va:", long_options,
-        getopt_long(argc, argv, "DVb:c:d:ehn:p:v", long_options, &option_index);
+                        &option_index);
     char *end;
     if (c == -1) {
       break;
     }
     switch (c) {
+    case 'a':
+      config.address = optarg;
+      break;
     case 'D':
       config.daemon = true;
       break;