wesommer@bacchus.UUCP (03/05/87)
Index: sys/netinet/tcp_input.c (4.3BSD, Ultrix 1.1)
Description:
If a packet to a TCP socket arrives in between the time that
the bind(2) call is done and the time a listen(2) call is done, the
socket behaves strangely; in particular, if the host trying to connect
to the socket is another BSD host, the listening socket is
mysteriously closed off after 45 seconds (the length of the TCP
keepalive timer); this bug is known to exist in 4.3BSD Beta, 4.3BSD
release, Ultrix 1.1, and Ultrix T2.0.
Repeat-By:
Compile the attached programs (server.c and client.c); then
start the server (which does the bind, sleeps 10 seconds, and then
does the listen) and then the client (within 10 seconds). Then wait a
minute or so; the server will start spewing error messages (returned
from the accept(2) system call).
Fix:
The problem is that tcp_input assumes that the presence of a
TCB means that the TCB is not closed, whereas a bind(2) call can
create a closed TCB which does not go into the LISTEN state until a
listen(2) call is done; if a packet comes in and matches the TCB, some
amount of input processing (including setting the keepalive timer) is
done on the packet and TCB before the kernel gives up. Apply the
enclosed patch (tcp_input.c.diff) to sys/netinet/tcp_input.c to solve
this problem.
Bill Sommerfeld
MIT Project Athena
ARPA: wesommer@athena.mit.edu
UUCP: ...!mit-eddie!wesommer
#! /bin/sh
# This is a shell archive, meaning:
# 1. Remove everything above the #! /bin/sh line.
# 2. Save the resulting text in a file.
# 3. Execute the file with /bin/sh (not csh) to create:
# Makefile
# client.c
# server.c
# tcp_input.c.diff
# This archive created: Wed Mar 4 21:26:33 1987
export PATH; PATH=/bin:/usr/bin:$PATH
echo shar: "extracting 'Makefile'" '(136 characters)'
if test -f 'Makefile'
then
echo shar: "will not over-write existing file 'Makefile'"
else
sed 's/^XX//' << \SHAR_EOF > 'Makefile'
XX
XXall: client server
XX
XXclient: client.o
XX cc -o client client.o
XX
XXserver: server.o
XX cc -o server server.o
XX
XXclean:
XX rm -f *.o client server
XX
SHAR_EOF
if test 136 -ne "`wc -c < 'Makefile'`"
then
echo shar: "error transmitting 'Makefile'" '(should have been 136 characters)'
fi
fi
echo shar: "extracting 'client.c'" '(1087 characters)'
if test -f 'client.c'
then
echo shar: "will not over-write existing file 'client.c'"
else
sed 's/^XX//' << \SHAR_EOF > 'client.c'
XX#include <sys/types.h>
XX#include <sys/socket.h>
XX#include <netinet/in.h>
XX#include <netdb.h>
XX#include <sys/param.h>
XX
XXmain()
XX{
XX struct sockaddr_in address;
XX struct hostent *hp;
XX int s;
XX char buf[10];
XX char hostname[MAXHOSTNAMELEN];
XX
XX if (gethostname(hostname, MAXHOSTNAMELEN) < 0) {
XX perror("gethostname");
XX exit(1);
XX }
XX if(!(hp = gethostbyname(hostname))) {
XX printf("Unknown host %s\n",hostname);
XX exit(1);
XX }
XX bzero((caddr_t)&address, sizeof(address));
XX
XX address.sin_family = AF_INET;
XX bcopy((caddr_t)hp->h_addr, (caddr_t)&address.sin_addr,
XX sizeof(struct in_addr));
XX address.sin_port = htons(3000);
XX
XX if ((s = socket(AF_INET, SOCK_STREAM,0)) < 0) {
XX perror("socket");
XX exit(1);
XX }
XX
XX if (connect(s, (caddr_t)&address, sizeof(address)) < 0) {
XX perror("connect");
XX exit(1);
XX }
XX printf("Reading..\n");
XX {
XX int count;
XX do {
XX if ((count = read(s, buf, sizeof(buf))) < 0) {
XX perror("read");
XX break;
XX }
XX if (count == 0) {
XX printf("End of file\n");
XX break;
XX }
XX printf("Read %d bytes\n", count);
XX } while (count > 0);
XX }
XX
XX printf("Exiting..\n");
XX exit(0);
XX}
SHAR_EOF
if test 1087 -ne "`wc -c < 'client.c'`"
then
echo shar: "error transmitting 'client.c'" '(should have been 1087 characters)'
fi
fi
echo shar: "extracting 'server.c'" '(793 characters)'
if test -f 'server.c'
then
echo shar: "will not over-write existing file 'server.c'"
else
sed 's/^XX//' << \SHAR_EOF > 'server.c'
XX#include <sys/types.h>
XX#include <sys/socket.h>
XX#include <netinet/in.h>
XX#include <netdb.h>
XX
XXmain()
XX{
XX struct sockaddr_in address;
XX int s;
XX
XX
XX if ((s = socket(AF_INET, SOCK_STREAM,0)) < 0) {
XX perror("socket");
XX exit(1);
XX }
XX bzero((caddr_t)&address, sizeof(address));
XX
XX address.sin_family = AF_INET;
XX address.sin_addr.s_addr = INADDR_ANY;
XX address.sin_port = htons(3000);
XX
XX if (bind(s, (caddr_t)&address, sizeof(address)) < 0) {
XX perror("bind");
XX exit(1);
XX }
XX printf("Sleeping.\n");
XX sleep(10);
XX if (listen(s, 5) < 0) {
XX perror("listen");
XX exit(1);
XX }
XX printf("Accepting.\n");
XX while(1) {
XX int len = sizeof(address);
XX int fd = accept(s, (caddr_t)&address, &len);
XX if (fd < 0) {
XX perror("accept");
XX continue;
XX }
XX printf("Accepted\n");
XX close(fd);
XX printf("Closed\n");
XX }
XX}
SHAR_EOF
if test 793 -ne "`wc -c < 'server.c'`"
then
echo shar: "error transmitting 'server.c'" '(should have been 793 characters)'
fi
fi
echo shar: "extracting 'tcp_input.c.diff'" '(850 characters)'
if test -f 'tcp_input.c.diff'
then
echo shar: "will not over-write existing file 'tcp_input.c.diff'"
else
sed 's/^XX//' << \SHAR_EOF > 'tcp_input.c.diff'
XX*** /tmp/,RCSt1026529 Wed Mar 4 21:23:16 1987
XX--- tcp_input.c Wed Mar 4 21:22:01 1987
XX***************
XX*** 173,180 ****
XX INPLOOKUP_WILDCARD);
XX
XX /*
XX! * If the state is CLOSED (i.e., TCB does not exist) then
XX! * all data in the incoming segment is discarded.
XX */
XX if (inp == 0)
XX goto dropwithreset;
XX--- 173,181 ----
XX INPLOOKUP_WILDCARD);
XX
XX /*
XX! * If the state is CLOSED (i.e., either the TCB does not exist or
XX! * the state is CLOSED) then all data in the incoming segment
XX! * is discarded.
XX */
XX if (inp == 0)
XX goto dropwithreset;
XX***************
XX*** 181,186 ****
XX--- 182,191 ----
XX tp = intotcpcb(inp);
XX if (tp == 0)
XX goto dropwithreset;
XX+ if (tp->t_state == TCPS_CLOSED) {
XX+ tp = 0;
XX+ goto dropwithreset;
XX+ }
XX so = inp->inp_socket;
XX if (so->so_options & SO_DEBUG) {
XX ostate = tp->t_state;
SHAR_EOF
if test 850 -ne "`wc -c < 'tcp_input.c.diff'`"
then
echo shar: "error transmitting 'tcp_input.c.diff'" '(should have been 850 characters)'
fi
fi
exit 0
# End of shell archive