Figure 2 Random TCP source ports (CONFIG_GRKERNSEC_RANDSRC)
[root@grsecurity root]# tcpdump -i lo dst port 5000 -w /tmp/output -c 2 & [1] 14764 tcpdump: listening on lo [root@grsecurity root]# telnet localhost 5000 Trying 127.0.0.1... telnet: connect to address 127.0.0.1: Connection refused [root@grsecurity root]# telnet localhost 5000 Trying 127.0.0.1... 4 packets received by filter 0 packets dropped by kernel telnet: connect to address 127.0.0.1: Connection refused [1]+ Done tcpdump -i lo dst port 5000 -w /tmp/output -c 2 [root@grsecurity root]# tcpdump -r /tmp/output 14:24:36.567312 localhost.50690 > localhost.5000: S 4010487236:4010487236(0) win 32767 <mss 16396,sackOK,timestamp 22457739 0,nop,wscale 0> (DF) [tos 0x10] 14:24:37.529007 localhost.33211 > localhost.5000: S 3051702410:3051702410(0) win 32767 <mss 16396,sackOK,timestamp 22457836 0,nop,wscale 0> (DF) [tos 0x10] --- [root@no-grsecurity root]# tcpdump -i lo dst port 5000 -w /tmp/output -c 2 & [1] 26922 tcpdump: listening on lo [root@d=no-grsecurity root]# telnet localhost 5000 Trying 127.0.0.1... telnet: connect to address 127.0.0.1: Connection refused [root@no-grsecurity root]# telnet localhost 5000 Trying 127.0.0.1... 4 packets received by filter 0 packets dropped by kernel telnet: connect to address 127.0.0.1: Connection refused [1]+ Done tcpdump -i lo dst port 5000 -w /tmp/output -c 2 [root@no-grsecurity root]# tcpdump -r /tmp/output 14:26:59.225768 localhost.localdomain.48533 > localhost.localdomain.5000: S 3264532978:3264532978(0) win 32767 <mss 16396,sackOK,timestamp 95383280 0,nop,wscale 0> (DF) [tos 0x10] 14:26:59.922787 localhost.localdomain.48534 > localhost.localdomain.5000: S 3264231394:3264231394(0) win 32767 <mss 16396,sackOK,timestamp 95383350 0,nop,wscale 0> (DF) [tos 0x10] |