diff options
| author | Peter Wu <peter@lekensteyn.nl> | 2016-08-10 17:23:16 +0200 |
|---|---|---|
| committer | Michael Kerrisk <mtk.manpages@gmail.com> | 2016-08-12 07:14:42 +1200 |
| commit | 3c3d1f83f9915f1e860c4e03f172ac9ab5d630bd (patch) | |
| tree | 778e07068442686212ba00048dc4678a56f57aa9 | |
| parent | 519303a6a4d455b8dc8d48ba1bcd510ce29d57f7 (diff) | |
| download | man-pages-3c3d1f83f9915f1e860c4e03f172ac9ab5d630bd.tar.gz | |
select_tut.2: fix issues in example
Avoid closing cfd if it is -1. Initialize buf1_avail, etc. to avoid
uninitialized memory access in the event that accept() fails. Remove
redundant setting of nfds. Fix tabs with spaces.
Do not try to read/write from/to file descriptors once an existing
connection is overwritten, the select() states are stale now.
Avoid writing zero bytes from the buffer and then closing the fd.
Signed-off-by: Peter Wu <peter@lekensteyn.nl>
| -rw-r--r-- | man2/select_tut.2 | 38 |
1 files changed, 18 insertions, 20 deletions
diff --git a/man2/select_tut.2 b/man2/select_tut.2 index 25dd3c6f58..7e4f41d7ea 100644 --- a/man2/select_tut.2 +++ b/man2/select_tut.2 @@ -594,7 +594,6 @@ connect_socket(int connect_port, char *address) cfd = socket(AF_INET, SOCK_STREAM, 0); if (cfd == \-1) { perror("socket"); - close(cfd); return \-1; } @@ -641,8 +640,8 @@ main(int argc, char *argv[]) int h; int fd1 = \-1, fd2 = \-1; char buf1[BUF_SIZE], buf2[BUF_SIZE]; - int buf1_avail, buf1_written; - int buf2_avail, buf2_written; + int buf1_avail = 0, buf1_written = 0; + int buf2_avail = 0, buf2_written = 0; if (argc != 4) { fprintf(stderr, "Usage\\n\\tfwd <listen\-port> " @@ -660,7 +659,7 @@ main(int argc, char *argv[]) for (;;) { int ready, nfds = 0; - ssize_t nbytes; + ssize_t nbytes; fd_set readfds, writefds, exceptfds; FD_ZERO(&readfds); @@ -668,22 +667,18 @@ main(int argc, char *argv[]) FD_ZERO(&exceptfds); FD_SET(h, &readfds); nfds = max(nfds, h); - if (fd1 > 0 && buf1_avail < BUF_SIZE) { + + if (fd1 > 0 && buf1_avail < BUF_SIZE) FD_SET(fd1, &readfds); - nfds = max(nfds, fd1); - } - if (fd2 > 0 && buf2_avail < BUF_SIZE) { + /* Note: nfds is updated below, when fd1 is added to exceptfds. */ + if (fd2 > 0 && buf2_avail < BUF_SIZE) FD_SET(fd2, &readfds); - nfds = max(nfds, fd2); - } - if (fd1 > 0 && buf2_avail \- buf2_written > 0) { + + if (fd1 > 0 && buf2_avail \- buf2_written > 0) FD_SET(fd1, &writefds); - nfds = max(nfds, fd1); - } - if (fd2 > 0 && buf1_avail \- buf1_written > 0) { + if (fd2 > 0 && buf1_avail \- buf1_written > 0) FD_SET(fd2, &writefds); - nfds = max(nfds, fd2); - } + if (fd1 > 0) { FD_SET(fd1, &exceptfds); nfds = max(nfds, fd1); @@ -706,9 +701,9 @@ main(int argc, char *argv[]) if (FD_ISSET(h, &readfds)) { socklen_t addrlen; struct sockaddr_in client_addr; - int fd; + int fd; - addrlen = sizeof(client_addr); + addrlen = sizeof(client_addr); memset(&client_addr, 0, addrlen); fd = accept(h, (struct sockaddr *) &client_addr, &addrlen); if (fd == \-1) { @@ -725,6 +720,9 @@ main(int argc, char *argv[]) else printf("connect from %s\\n", inet_ntoa(client_addr.sin_addr)); + + /* Skip any events on the old, closed file descriptors. */ + continue; } } @@ -764,7 +762,7 @@ main(int argc, char *argv[]) else buf2_avail += nbytes; } - if (fd1 > 0 && FD_ISSET(fd1, &writefds)) { + if (fd1 > 0 && FD_ISSET(fd1, &writefds) && buf2_avail > 0) { nbytes = write(fd1, buf2 + buf2_written, buf2_avail \- buf2_written); if (nbytes < 1) @@ -772,7 +770,7 @@ main(int argc, char *argv[]) else buf2_written += nbytes; } - if (fd2 > 0 && FD_ISSET(fd2, &writefds)) { + if (fd2 > 0 && FD_ISSET(fd2, &writefds) && buf1_avail > 0) { nbytes = write(fd2, buf1 + buf1_written, buf1_avail \- buf1_written); if (nbytes < 1) |