CODEWITHSUNDEEP
c++linuxnetwork-programmingmulticast
R_N
R_N

Reputation: 111

Change TTL from application on linux

is there a way to set ttl from application? Using c++ rh, not using boost. In /etc/sysctl.conf file value net.ipv4.ip_default_ttl is not present, in /proc/sys/net/ipv4/ip_default_ttl written 64. I am sending traffic to multicast group and see TTL=1. Would like to increase it to 3. Thanks.

Upvotes: 1

Views: 1811

Answers (1)

Kristof Provost
Kristof Provost

Reputation: 26332

You can configure it per socket, using the IP_MULTICAST_TTL setsockopt() flag. Take a look at the man pages for ip and setsockopt.

Something like the following:

void setttl(int sock, uint8_t ttl)
{
    int ret = setsockopt(sock, IPPROTO_IP, IP_MULTICAST_TTL, &ttl, sizeof(uint8_t));
    if (ret != 0)
        printf("Failed to setsockopt(): %s\n", strerror(errno));
}

Upvotes: 3

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