add support for reverse port lookups from services file to getnameinfo

this also affects the legacy getservbyport family, which uses
getnameinfo as its backend.

diff --git a/src/network/getnameinfo.c b/src/network/getnameinfo.c
index 708ec5e..588ed76 100644 (file)
--- a/src/network/getnameinfo.c
+++ b/src/network/getnameinfo.c
@@ -45,13 +45,13 @@ static void mkptr6(char *s, const unsigned char *ip)
        strcpy(s, "ip6.arpa");
 }
 
-static char *reverse_hosts(char *buf, const unsigned char *a, unsigned scopeid, int family)
+static void reverse_hosts(char *buf, const unsigned char *a, unsigned scopeid, int family)
 {
        char line[512], *p, *z;
        unsigned char _buf[1032], atmp[16];
        struct address iplit;
        FILE _f, *f = __fopen_rb_ca("/etc/hosts", &_f, _buf, sizeof _buf);
-       if (!f) return 0;
+       if (!f) return;
        if (family == AF_INET) {
                memcpy(atmp+12, a, 4);
                memcpy(atmp, "\0\0\0\0\0\0\0\0\0\0\xff\xff", 12);
@@ -83,7 +83,32 @@ static char *reverse_hosts(char *buf, const unsigned char *a, unsigned scopeid,
                }
        }
        __fclose_ca(f);
-       return 0;
+}
+
+static void reverse_services(char *buf, int port, int dgram)
+{
+       unsigned long svport;
+       char line[128], *p, *z;
+       unsigned char _buf[1032];
+       FILE _f, *f = __fopen_rb_ca("/etc/services", &_f, _buf, sizeof _buf);
+       if (!f) return;
+       while (fgets(line, sizeof line, f)) {
+               if ((p=strchr(line, '#'))) *p++='\n', *p=0;
+
+               for (p=line; *p && !isspace(*p); p++);
+               if (!p) continue;
+               *p++ = 0;
+               svport = strtoul(p, &z, 10);
+
+               if (svport != port || z==p) continue;
+               if (dgram && strncmp(z, "/udp", 4)) continue;
+               if (!dgram && strncmp(z, "/tcp", 4)) continue;
+               if (p-line > 32) continue;
+
+               memcpy(buf, line, p-line);
+               break;
+       }
+       __fclose_ca(f);
 }
 
 static int dns_parse_callback(void *c, int rr, const void *data, int len, const void *packet)
@@ -162,7 +187,13 @@ int getnameinfo(const struct sockaddr *restrict sa, socklen_t sl,
        }
 
        if (serv && servlen) {
-               char *p = itoa(num, ntohs(((struct sockaddr_in *)sa)->sin_port));
+               char *p = buf;
+               int port = ntohs(((struct sockaddr_in *)sa)->sin_port);
+               buf[0] = 0;
+               if (!(flags & NI_NUMERICSERV))
+                       reverse_services(buf, port, flags & NI_DGRAM);
+               if (!*p)
+                       p = itoa(num, port);
                if (strlen(p) >= servlen)
                        return EAI_OVERFLOW;
                strcpy(serv, p);