nginx源码分析（5）——监听socket初始化
在nginx源码分析（4）中，看到了nginx的事件模型，但其中没有介绍监听socket的初始化。而对于web server来说，需要通过监听socket来监听客户端的连接等。本篇将会具体介绍这方面的内容。还记得在前文介绍ngx_cycle_t结构时，它具有一个listening属性，是一个数组，存储所有监听socket，下面就来看看这些信息是什么时候添加的、以及如何初始化的。
1. 重要的数据结构1. ngx_http_conf_port_t
监听端口配置信息，addrs是在该端口上所有监听地址的数组。
voidngx_configure_listening_sockets(ngx_cycle_t *cycle){ ngx_uint_t i; ngx_listening_t *ls;#if (NGX_HAVE_DEFERRED_ACCEPT && defined SO_ACCEPTFILTER) struct accept_filter_arg af;#endif#if (NGX_HAVE_DEFERRED_ACCEPT && defined TCP_DEFER_ACCEPT) int timeout;#endif ls = cycle->listening.elts; for (i = 0; i < cycle->listening.nelts; i++) { ls[i].log = *ls[i].logp; /** * 设置监听socket的接收缓冲区大小 */ if (ls[i].rcvbuf != -1) { if (setsockopt(ls[i].fd, SOL_SOCKET, SO_RCVBUF, (const void *) &ls[i].rcvbuf, sizeof(int)) == -1) { ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_socket_errno, "setsockopt(SO_RCVBUF, %d) %V failed, ignored", ls[i].rcvbuf, &ls[i].addr_text); } } /** * 设置监听socket的发送缓冲区大小 */ if (ls[i].sndbuf != -1) { if (setsockopt(ls[i].fd, SOL_SOCKET, SO_SNDBUF, (const void *) &ls[i].sndbuf, sizeof(int)) == -1) { ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_socket_errno, "setsockopt(SO_SNDBUF, %d) %V failed, ignored", ls[i].sndbuf, &ls[i].addr_text); } }#if (NGX_HAVE_SETFIB) if (ls[i].setfib != -1) { if (setsockopt(ls[i].fd, SOL_SOCKET, SO_SETFIB, (const void *) &ls[i].setfib, sizeof(int)) == -1) { ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_socket_errno, "setsockopt(SO_SETFIB, %d) %V failed, ignored", ls[i].setfib, &ls[i].addr_text); } }#endif#if 0 if (1) { int tcp_nodelay = 1; if (setsockopt(ls[i].fd, IPPROTO_TCP, TCP_NODELAY, (const void *) &tcp_nodelay, sizeof(int)) == -1) { ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_socket_errno, "setsockopt(TCP_NODELAY) %V failed, ignored", &ls[i].addr_text); } }#endif if (ls[i].listen) { /* change backlog via listen() */ if (listen(ls[i].fd, ls[i].backlog) == -1) { ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_socket_errno, "listen() to %V, backlog %d failed, ignored", &ls[i].addr_text, ls[i].backlog); } } /* * setting deferred mode should be last operation on socket, * because code may prematurely continue cycle on failure */#if (NGX_HAVE_DEFERRED_ACCEPT)#ifdef SO_ACCEPTFILTER if (ls[i].delete_deferred) { /** * set accept filter on listening socket * 将SO_ACCEPTFILTER设置为NULL，也就是删除accept filter */ if (setsockopt(ls[i].fd, SOL_SOCKET, SO_ACCEPTFILTER, NULL, 0) == -1) { ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno, "setsockopt(SO_ACCEPTFILTER, NULL) " "for %V failed, ignored", &ls[i].addr_text); if (ls[i].accept_filter) { ngx_log_error(NGX_LOG_ALERT, cycle->log, 0, "could not change the accept filter " "to \"%s\" for %V, ignored", ls[i].accept_filter, &ls[i].addr_text); } continue; } ls[i].deferred_accept = 0; } if (ls[i].add_deferred) { ngx_memzero(&af, sizeof(struct accept_filter_arg)); (void) ngx_cpystrn((u_char *) af.af_name, (u_char *) ls[i].accept_filter, 16); /** * set accept filter on listening socket * 将SO_ACCEPTFILTER设置为ls[i].accept_filter，也就是添加accept filter */ if (setsockopt(ls[i].fd, SOL_SOCKET, SO_ACCEPTFILTER, &af, sizeof(struct accept_filter_arg)) == -1) { ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno, "setsockopt(SO_ACCEPTFILTER, \"%s\") " " for %V failed, ignored", ls[i].accept_filter, &ls[i].addr_text); continue; } ls[i].deferred_accept = 1; }#endif#ifdef TCP_DEFER_ACCEPT if (ls[i].add_deferred || ls[i].delete_deferred) { if (ls[i].add_deferred) { timeout = (int) (ls[i].post_accept_timeout / 1000); } else { timeout = 0; } if (setsockopt(ls[i].fd, IPPROTO_TCP, TCP_DEFER_ACCEPT, &timeout, sizeof(int)) == -1) { ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno, "setsockopt(TCP_DEFER_ACCEPT, %d) for %V failed, " "ignored", timeout, &ls[i].addr_text); continue; } } if (ls[i].add_deferred) { ls[i].deferred_accept = 1; }#endif#endif /* NGX_HAVE_DEFERRED_ACCEPT */ } return;} 这个函数就是根据配置调用setsockopt函数设置socket选项，比如接收缓冲区、发送缓冲区等，具体也没有什么可讲的。