stuff from chiark:/usr/local/src/misc/ (as found)

[chiark-utils.git] / cprogs / smtpallow.c

diff --git a/cprogs/smtpallow.c b/cprogs/smtpallow.c
new file mode 100644 (file)
index 0000000..d8c8532
--- /dev/null
+++ b/cprogs/smtpallow.c
@@ -0,0 +1,44 @@
+/**/
+
+#include <syscall.h>
+#include <sys/socketcall.h>
+#include <netinet/in.h>
+#include <string.h>
+
+_syscall2(long,socketcall,int,call,unsigned long *,args);
+
+int real_connect(int sockfd, const struct sockaddr *saddr, int addrlen)
+{
+       unsigned long args[3];
+
+       args[0] = sockfd;
+       args[1] = (unsigned long)saddr;
+       args[2] = addrlen;
+       return socketcall(SYS_CONNECT, args);
+}
+
+int connect(int fd, const struct sockaddr *them_any, int addrlen) {
+  struct sockaddr_in *them= (struct sockaddr_in*)them_any;
+  int r,l,i;
+  struct sockaddr_in us;
+  
+  if (addrlen == sizeof(us) &&
+      them->sin_family == AF_INET &&
+      them->sin_port == htons(25)) {
+    memset(&us,0,sizeof(us));
+    us.sin_port= 0;
+    us.sin_family= AF_INET;
+    us.sin_addr.s_addr= INADDR_ANY;
+    r= getsockname(fd,(struct sockaddr*)&us,&l);
+    if (r<0 && errno != EINVAL) return r;
+    if (!ntohs(us.sin_port)) {
+      for (i=1023; i>0; i--) {
+        us.sin_port= htons(i);
+        if (!bind(fd,(struct sockaddr*)&us,sizeof(us))) break;
+        if (errno != EADDRINUSE) return -1;
+      }
+      if (!i) return -1;
+    } else if (r<0) return r;
+  }
+  return real_connect(fd,them_any,addrlen);
+}