#include "../../include/bpf_api.h" /* This example demonstrates how classifier run-time behaviour * can be altered with tail calls. We start out with an empty * jmp_tc array, then add section aaa to the array slot 0, and * later on atomically replace it with section bbb. Note that * as shown in other examples, the tc loader can prepopulate * tail called sections, here we start out with an empty one * on purpose to show it can also be done this way. * * tc filter add dev foo parent ffff: bpf obj graft.o * tc exec bpf dbg * [...] * Socket Thread-20229 [001] ..s. 138993.003923: : fallthrough * <idle>-0 [001] ..s. 138993.202265: : fallthrough * Socket Thread-20229 [001] ..s. 138994.004149: : fallthrough * [...] * * tc exec bpf graft m:globals/jmp_tc key 0 obj graft.o sec aaa * tc exec bpf dbg * [...] * Socket Thread-19818 [002] ..s. 139012.053587: : aaa * <idle>-0 [002] ..s. 139012.172359: : aaa * Socket Thread-19818 [001] ..s. 139012.173556: : aaa * [...] * * tc exec bpf graft m:globals/jmp_tc key 0 obj graft.o sec bbb * tc exec bpf dbg * [...] * Socket Thread-19818 [002] ..s. 139022.102967: : bbb * <idle>-0 [002] ..s. 139022.155640: : bbb * Socket Thread-19818 [001] ..s. 139022.156730: : bbb * [...] */ BPF_PROG_ARRAY(jmp_tc, 0, PIN_GLOBAL_NS, 1); __section("aaa") int cls_aaa(struct __sk_buff *skb) { char fmt[] = "aaa\n"; trace_printk(fmt, sizeof(fmt)); return TC_H_MAKE(1, 42); } __section("bbb") int cls_bbb(struct __sk_buff *skb) { char fmt[] = "bbb\n"; trace_printk(fmt, sizeof(fmt)); return TC_H_MAKE(1, 43); } __section_cls_entry int cls_entry(struct __sk_buff *skb) { char fmt[] = "fallthrough\n"; tail_call(skb, &jmp_tc, 0); trace_printk(fmt, sizeof(fmt)); return BPF_H_DEFAULT; } BPF_LICENSE("GPL");