One - The Linux Kernel Archives

More documents

Recommendations

Info

14 • Linux Symposium 2004 • Volume One for the connection in question by getting the TCP_MAXICISIZE socket option. Example: void *buf; int ici_size; size_t size = sizeof(int); getsockopt(s,SOL_TCP,TCP_MAXICISIZE, &ici_size,&size); buf = malloc(ici_size); size = ici_size; getsockopt(s,SOL_TCP,TCP_ICI, buf,&size); The connection endpoint at the destination is created by setting the TCP_ICI socket option, and the connection is activated by “setting” the TCP_CP_FN socket option to the value TCPCP_ACTIVATE. 1 Example: int sub_function = TCPCP_ACTIVATE; setsockopt(s,SOL_TCP,TCP_ICI, buf,size); /* ... */ setsockopt(s,SOL_TCP,TCP_CP_FN, &sub_function, sizeof(sub_function)); 3.2 High-level API These are the most important functions provided by the high-level API: void *tcpcp_get(int s); int tcpcp_size(const void *ici); int tcpcp_create(const void *ici); int tcpcp_activate(int s); 1 The use of a multiplexed socket option is admittedly ugly, although convenient during development. tcpcp_get allocates a buffer for the ICI, and retrieves that ICI (isolating the connection as a side-effect). The amount of data in the ICI can be queried by calling tcpcp_size on it. tcpcp_create sets an ICI on a socket, and tcpcp_activate activates the connection. 4 Describing a TCP endpoint In this section, we describe the parameters that define a TCP connection and its state. tcpcp collects all the information it needs to re-create a TCP connection endpoint in a data structure we call Internal Connection Information (ICI). The ICI is portable among systems supporting tcpcp, irrespective of their CPU architecture. Besides this data, the kernel maintains a large number of additional variables that can either be reset to default values at the destination (such as congestion control state), or that are only rarely used and not essential for correct operation of TCP (such as statistics). 4.1 Connection identifier Each TCP connection in the global Internet or any private internet [9] is uniquely identified by the IP addresses of the source and destination host, and the port numbers used at both ends. tcpcp currently only supports IPv4, but can be extended to support IPv6, should the need arise. 4.2 Fixed data A few parameters of a TCP connection are negotiated during the initial handshake, and remain unchanged during the life time of the connection. These parameters include whether window scaling, timestamps, or selective acknowledgments are used, the number of bits by
Linux Symposium 2004 • Volume One • 15 Connection identifier ip.v4.ip_src IPv4 address of the host on which the ICI was recorded (source) ip.v4.ip_dst IPv4 address of the peer (destination) tcp_sport Port at the source host tcp_dport Port at the destination host Fixed at connection setup tcp_flags TCP flags (window scale, SACK, ECN, etc.) snd_wscale Send window scale rcv_wscale Receive window scale snd_mss Maximum Segment Size at the source host rcv_mss MSS at the destination host Connection state state TCP connection state (e.g. ESTABLISHED) Sequence numbers snd_nxt Sequence number of next new byte to send rcv_nxt Sequence number of next new byte expected to receive Windows (flow-control) snd_wnd Window received from peer rcv_wnd Window advertised to peer Timestamps ts_gen Current value of the timestamp generator ts_recent Most recently received timestamp Table 1: TCP variables recorded in tcpcp’s Internal Connection Information (ICI) structure. which the window is shifted, and the maximum segment sizes (MSS). These parameters are used mainly for sanity checks, and to determine whether the destination host is able to handle the connection. The received MSS continues of course to limit the segment size. 4.3 Sequence numbers The sequence numbers are used to synchronize all aspects of a TCP connection. Only the sequence numbers we expect to see in the network, in either direction, are needed when re-creating the endpoint. The kernel uses several variables that are derived from these sequence numbers. The values of these variables either coincide with snd_nxt and rcv_nxt in the state we set up, or they can be calculated by examining the send buffer. 4.4 Windows (flow-control) The (flow-control) window determines how much more data can be sent or received without overrunning the receiver’s buffer. The window the origin received from the peer is also the window we can use after re-creating the endpoint. The window the origin advertised to the peer defines the minimum receive buffer size at the destination.
Page 1: Proceedings of the Linux Symposium
Page 4 and 5: The State of ACPI in the Linux Kern
Page 7 and 8: Conference Organizers Andrew J. Hut
Page 9 and 10: TCP Connection Passing Werner Almes
Page 11 and 12: Linux Symposium 2004 • Volume One
Page 13: Linux Symposium 2004 • Volume One
Page 23 and 24: Cooperative Linux Dan Aloni da-x@co
Page 33 and 34: Build your own Wireless Access Poin
Page 41 and 42: Run-time testing of LSB Application
Page 51 and 52: Linux Block IO—present and future
Page 63 and 64: Linux AIO Performance and Robustnes
Page 65 and 66:
Linux Symposium 2004 • Volume One
Page 67 and 68:
Page 69 and 70:
Page 71 and 72:
Page 73 and 74:
Page 75 and 76:
Page 77 and 78:
Page 79 and 80:
Methods to Improve Bootup Time in L
Page 81 and 82:
Page 83 and 84:
Page 85 and 86:
Page 87 and 88:
Page 89 and 90:
Linux on NUMA Systems Martin J. Bli
Page 91 and 92:
Page 93 and 94:
Page 95 and 96:
Page 97 and 98:
Page 99 and 100:
Page 101 and 102:
Page 103 and 104:
Improving Kernel Performance by Unm
Page 105 and 106:
Page 107 and 108:
Page 109 and 110:
Page 111 and 112:
Page 113 and 114:
Linux Virtualization on IBM POWER5
Page 115 and 116:
Page 117 and 118:
Page 119 and 120:
Page 121 and 122:
The State of ACPI in the Linux Kern
Page 123 and 124:
Page 125 and 126:
Page 127 and 128:
Page 129 and 130:
Page 131 and 132:
Page 133 and 134:
Scaling Linux® to the Extreme From
Page 135 and 136:
Page 137 and 138:
Page 139 and 140:
Page 141 and 142:
Page 143 and 144:
Page 145 and 146:
Page 147 and 148:
Page 149 and 150:
Get More Device Drivers out of the
Page 151 and 152:
Page 153 and 154:
Page 155 and 156:
Page 157 and 158:
Page 159 and 160:
Page 161 and 162:
Page 163 and 164:
Big Servers—2.6 compared to 2.4 W
Page 165 and 166:
Page 167 and 168:
Multi-processor and Frequency Scali
Page 169 and 170:
Page 171 and 172:
Page 173 and 174:
Page 175 and 176:
Page 177 and 178:
Page 179 and 180:
Page 181 and 182:
Page 183 and 184:
Page 185 and 186:
Page 187 and 188:
Dynamic Kernel Module Support: From
Page 189 and 190:
Page 191 and 192:
Page 193 and 194:
Page 195 and 196:
Page 197 and 198:
Page 199 and 200:
Page 201 and 202:
Page 203 and 204:
e100 Weight Reduction Program Writi
Page 205 and 206:
Page 207 and 208:
NFSv4 and rpcsec_gss for linux J. B
Page 209 and 210:
Page 211 and 212:
Page 213 and 214:
Page 215 and 216:
Comparing and Evaluating epoll, sel
Page 217 and 218:
Page 219 and 220:
Page 221 and 222:
Page 223 and 224:
Page 225 and 226:
Page 227 and 228:
The (Re)Architecture of the X Windo
Page 229 and 230:
Page 231 and 232:
Page 233 and 234:
Page 235 and 236:
Page 237 and 238:
Page 239 and 240:
IA64-Linux perf tools for IO dorks
Page 241 and 242:
Page 243 and 244:
Page 245 and 246:
Page 247 and 248:
Page 249 and 250:
Page 251 and 252:
Page 253 and 254:
Page 255 and 256:
Carrier Grade Server Features in th
Page 257 and 258:
Page 259 and 260:
Page 261 and 262:
Page 263 and 264:
Page 265 and 266:
Page 267 and 268:
Page 269 and 270:
Demands, Solutions, and Improvement
Page 271 and 272:
Page 273 and 274:
Page 275 and 276:
Page 277 and 278:
Page 279 and 280:
Page 281 and 282:
Page 283 and 284:
Page 285 and 286:
Page 287 and 288:
Hotplug Memory and the Linux VM Dav
Page 289 and 290:
Page 291 and 292:
Page 293 and 294:
show all

One - The Linux Kernel Archives

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?