1/* $NetBSD: sane_accept.c,v 1.2 2017/02/14 01:16:49 christos Exp $ */ 2 3/*++ 4/* NAME 5/* sane_accept 3 6/* SUMMARY 7/* sanitize accept() error returns 8/* SYNOPSIS 9/* #include <sane_accept.h> 10/* 11/* int sane_accept(sock, buf, len) 12/* int sock; 13/* struct sockaddr *buf; 14/* SOCKADDR_SIZE *len; 15/* DESCRIPTION 16/* sane_accept() implements the accept(2) socket call, and maps 17/* known harmless error results to EAGAIN. 18/* 19/* If the buf and len arguments are not null, then additional 20/* workarounds may be enabled that depend on the socket type. 21/* BUGS 22/* Bizarre systems may have other harmless error results. Such 23/* systems encourage programmers to ignore error results, and 24/* penalize programmers who code defensively. 25/* LICENSE 26/* .ad 27/* .fi 28/* The Secure Mailer license must be distributed with this software. 29/* AUTHOR(S) 30/* Wietse Venema 31/* IBM T.J. Watson Research 32/* P.O. Box 704 33/* Yorktown Heights, NY 10598, USA 34/*--*/ 35 36/* System library. */ 37 38#include "sys_defs.h" 39#include <sys/socket.h> 40#include <errno.h> 41 42/* Utility library. */ 43 44#include "msg.h" 45#include "sane_accept.h" 46 47/* sane_accept - sanitize accept() error returns */ 48 49int sane_accept(int sock, struct sockaddr *sa, SOCKADDR_SIZE *len) 50{ 51 static int accept_ok_errors[] = { 52 EAGAIN, 53 ECONNREFUSED, 54 ECONNRESET, 55 EHOSTDOWN, 56 EHOSTUNREACH, 57 EINTR, 58 ENETDOWN, 59 ENETUNREACH, 60 ENOTCONN, 61 EWOULDBLOCK, 62 ENOBUFS, /* HPUX11 */ 63 ECONNABORTED, 64#ifdef EPROTO 65 EPROTO, /* SunOS 5.5.1 */ 66#endif 67 0, 68 }; 69 int count; 70 int err; 71 int fd; 72 73 /* 74 * XXX Solaris 2.4 accept() returns EPIPE when a UNIX-domain client has 75 * disconnected in the mean time. From then on, UNIX-domain sockets are 76 * hosed beyond recovery. There is no point treating this as a beneficial 77 * error result because the program would go into a tight loop. 78 * 79 * XXX Solaris 2.5.1 accept() returns EPROTO when a TCP client has 80 * disconnected in the mean time. Since there is no connection, it is 81 * safe to map the error code onto EAGAIN. 82 * 83 * XXX LINUX < 2.1 accept() wakes up before the three-way handshake is 84 * complete, so it can fail with ECONNRESET and other "false alarm" 85 * indications. 86 * 87 * XXX FreeBSD 4.2-STABLE accept() returns ECONNABORTED when a UNIX-domain 88 * client has disconnected in the mean time. The data that was sent with 89 * connect() write() close() is lost, even though the write() and close() 90 * reported successful completion. This was fixed shortly before FreeBSD 91 * 4.3. 92 * 93 * XXX HP-UX 11 returns ENOBUFS when the client has disconnected in the mean 94 * time. 95 */ 96 if ((fd = accept(sock, sa, len)) < 0) { 97 for (count = 0; (err = accept_ok_errors[count]) != 0; count++) { 98 if (errno == err) { 99 errno = EAGAIN; 100 break; 101 } 102 } 103 } 104 105 /* 106 * XXX Solaris select() produces false read events, so that read() blocks 107 * forever on a blocking socket, and fails with EAGAIN on a non-blocking 108 * socket. Turning on keepalives will fix a blocking socket provided that 109 * the kernel's keepalive timer expires before the Postfix watchdog 110 * timer. 111 * 112 * XXX Work around NAT induced damage by sending a keepalive before an idle 113 * connection is expired. This requires that the kernel keepalive timer 114 * is set to a short time, like 100s. 115 */ 116 else if (sa && (sa->sa_family == AF_INET 117#ifdef HAS_IPV6 118 || sa->sa_family == AF_INET6 119#endif 120 )) { 121 int on = 1; 122 123 (void) setsockopt(fd, SOL_SOCKET, SO_KEEPALIVE, 124 (void *) &on, sizeof(on)); 125 } 126 return (fd); 127} 128