On Mon, 20 May 2024 14:05:58 +0530 Danish Prakash <contact(a)danishpraka.sh> wrote:When invoking pasta without any arguments, it's difficult to tell whether we are in the new namespace or not leaving users a bit confused. This change modifies the host namespace to add a prefix "pasta-" to make it a bit more obvious.Thanks for the patch, it works for me: sbrivio@maja:~/passt$ ./pasta --config-net root@pasta-maja:~/passt# ./pasta --config-net root@pasta-pasta-maja:~/passt# ./pasta --config-net root@pasta-pasta-pasta-maja:~/passt# ./pasta --config-net root@pasta-pasta-pasta-pasta-maja:~/passt# ./pasta --config-net root@pasta-pasta-pasta-pasta-pasta-maja:~/passt# ./pasta --config-net root@pasta-pasta-pasta-pasta-pasta-pasta-maja:~/passt# ./pasta --config-net root@pasta-pasta-pasta-pasta-pasta-pasta-pasta-maja:~/passt# ./pasta --config-net root@pasta-pasta-pasta-pasta-pasta-pasta-pasta-pasta-maja:~/passt# ./pasta --config-net root@pasta-pasta-pasta-pasta-pasta-pasta-pasta-pasta-pasta-maja:~/passt# ./pasta --config-net root@pasta-pasta-pasta-pasta-pasta-pasta-pasta-pasta-pasta-pasta-maja:~/passt# ./pasta --config-net root@pasta-pasta-pasta-pasta-pasta-pasta-pasta-pasta-pasta-pasta-past:~/passt# a few comments (all about brevity and style), below:Signed-off-by: Danish Prakash <contact(a)danishpraka.sh> --- pasta.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/pasta.c b/pasta.c index 31e1e00..840a2b1 100644 --- a/pasta.c +++ b/pasta.c @@ -180,6 +180,8 @@ static int pasta_spawn_cmd(void *arg) { const struct pasta_spawn_cmd_arg *a; sigset_t set; + char hostname[HOST_NAME_MAX+1], pasta_hostname[HOST_NAME_MAX+1];For coding style consistency: "HOST_NAME_MAX + 1" (with spaces).+ char *hostname_prefix = "pasta-";In passt, which follows the coding style of the Linux kernel for the networking part, we order variables from the longest to the shortest. Rationale: https://hisham.hm/2018/06/16/when-listing-repeated-things-make-pyramids/ see also https://lwn.net/Articles/758552/. But actually, you don't need more than one variable here, see below./* We run in a detached PID and mount namespace: mount /proc over */ if (mount("", "/proc", "proc", 0, NULL)) @@ -188,6 +190,17 @@ static int pasta_spawn_cmd(void *arg) if (write_file("/proc/sys/net/ipv4/ping_group_range", "0 0")) warn("Cannot set ping_group_range, ICMP requests might fail"); + if (gethostname(hostname, HOST_NAME_MAX+1) == 0) {In general, unless one wants to stress that the return value could be a number of positive or negative values, we just use for the common case (0: success, -1: error): if (!gethostname(...)) {+ if ((strlen(hostname) + strlen(hostname_prefix)) > HOST_NAME_MAX) { + hostname[strlen(hostname)-strlen(hostname_prefix)] = '\0'; + }For consistency: no curly brackets for statements that fit a single line.+ sprintf(pasta_hostname, "%s%s", hostname_prefix, hostname);You could drop all this if you initialise the target variable directly, say: char hostname[HOST_NAME_MAX + 1] = "pasta-"; then you can gethostname() on it + sizeof("pasta-") - 1 (NULL terminating byte returned by sizeof()), directly. Using a #define for "pasta-": gethostname(hostname + sizeof(HOSTNAME_PREFIX) - 1, HOST_NAME_MAX + 1 - sizeof(HOSTNAME_PREFIX));+ + if (sethostname(pasta_hostname, strlen(pasta_hostname)) != 0) {Same here about !sethostname() vs. sethostname() != 0, and curly brackets.+ warn("Unable to set pasta-prefixed hostname"); + } + } + /* Wait for the parent to be ready: see main() */ sigemptyset(&set); sigaddset(&set, SIGUSR1);-- Stefano