Date: Sat, 28 Feb 1998 13:36:14 PST From: Bill Fenner <fenner@parc.xerox.com> To: FreeBSD-gnats-submit@FreeBSD.ORG Subject: kern/5877: sb_cc counts control data as well as data data Message-ID: <199802282136.NAA04591@fenestro.parc.xerox.com>
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>Number: 5877 >Category: kern >Synopsis: sb_cc counts control data as well as data data >Confidential: no >Severity: serious >Priority: medium >Responsible: freebsd-bugs >State: open >Quarter: >Keywords: >Date-Required: >Class: sw-bug >Submitter-Id: current-users >Arrival-Date: Sat Feb 28 13:40:00 PST 1998 >Last-Modified: >Originator: Bill Fenner >Organization: Xerox >Release: FreeBSD 3.0-CURRENT i386 >Environment: BSD since the beginning of time (well, 4.2 =) >Description: A socket's sb_cc field includes the length of control data (like the source address, for PR_ADDR protocols, and any control info like if SO_TIMESTAMP, IP_RECVIF, etc. are set). Problems with this include: - FIONREAD just returns sb_cc, but not all these bytes are readable - This count is used to determine the high/low water marks on the socket. Advantages are: - sb_cc is really the length of the attached mbufs, so it's simple to compute. >How-To-Repeat: Adel Abushaev <adel@ksu.ru> reported the problem and included this pair of test programs. /* client.c */ #include <stdio.h> #include <sys/types.h> #include <sys/time.h> #include <sys/socket.h> #include <netinet/in.h> #include <arpa/inet.h> void main() { int sockfd; struct sockaddr_in servaddr_in; char buffer[512]; memset(&servaddr_in, 0, sizeof(struct sockaddr_in)); servaddr_in.sin_family = AF_INET; servaddr_in.sin_addr.s_addr = inet_addr("127.0.0.1"); servaddr_in.sin_port = htons(4000); sockfd = socket(AF_INET, SOCK_DGRAM, 0); if (sockfd <= 0) { perror("socket"); return; } sendto(sockfd, buffer, 512, 0, (struct sockaddr *)&servaddr_in, sizeof(struct sockaddr_in)); close(sockfd); } /* server.c */ #include <stdio.h> #include <sys/types.h> #include <sys/time.h> #include <sys/socket.h> #include <netinet/in.h> #include <arpa/inet.h> #include <sys/stat.h> #include <sys/fcntl.h> #include <sys/ioctl.h> #ifdef SOLARIS #include <sys/filio.h> #endif void main() { int sockfd; struct sockaddr_in myaddr_in, peeraddr_in; unsigned addrlen; char buffer[512]; struct timeval tim; int optval; fd_set fdsread, fdswrite, fdsexcept; memset(&myaddr_in, 0, sizeof(struct sockaddr_in)); memset(&peeraddr_in, 0, sizeof(struct sockaddr_in)); myaddr_in.sin_family = AF_INET; myaddr_in.sin_addr.s_addr = INADDR_ANY; myaddr_in.sin_port = htons(4000); sockfd = socket(AF_INET, SOCK_DGRAM, 0); if (sockfd <= 0) { perror("socket"); return; } if (bind(sockfd, (struct sockaddr *)&myaddr_in, sizeof(struct sockaddr_in)) < 0) { perror("bind"); return; } FD_ZERO(&fdsread); FD_ZERO(&fdswrite); FD_ZERO(&fdsexcept); FD_SET(sockfd, &fdsread); tim.tv_sec=60; tim.tv_usec=0; select(sockfd+1, &fdsread, &fdswrite, &fdsexcept, &tim); if (FD_ISSET(sockfd, &fdsread)) { ioctl(sockfd, FIONREAD, &optval); printf("ioctl: %d\n",optval); optval=recvfrom(sockfd, buffer, 512, 0, (struct sockaddr *)&peeraddr_in, &addrlen); printf("recv: %d\n",optval); ioctl(sockfd, FIONREAD, &optval); printf("ioctl: %d\n",optval); } close(sockfd); } >Fix: Make sb_cc reflect the number of data bytes in the socket buffer, instead of the amount of data+control. This may be as simple as fixing sballoc() and sbfree() in sys/socketvar.h to only count MT_HEADER, MT_DATA, MT_OOBDATA mbufs, or may be much more involved. >Audit-Trail: >Unformatted: To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-bugs" in the body of the message
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